Littelfuse S PROTECTION RELAYS & CONTROLS CATALOG

). While fuses can protect against phase-to-phase faults, additional protection, such as protection relays, are typically required to protect against ground faults. Definition of Ground Fault A ground fault is an inadvertent contact between an energized conductor and ground or the equipment frame. The return path of the fault current is through the grounding system and any equipment or personnel that becomes part of that system. Ground faults are frequently the result of insulation breakdown. It’s important to note that damp, wet, and dusty environments require extra diligence in design and maintenance. Since contaminated water is conductive, it exposes degradation of insulation and increases the potential for hazards to develop. Table 1 shows the leading initiators of electrical faults. LEADING INITIATORS OF FAULTS % OF ALL FAULTS Exposure to moisture 22.5% Shorting by tools, rodents, etc. 18.0% Exposure to dust 14.5% Other mechanical damage 12.1% Exposure to chemicals 9.0% Normal deterioration from age 7.0% TABLE 1 PROTECTION OVERVIEW 15 © 2022 Littelfuse, Inc. 515 Littelfuse.com/relayscontrols Overview Ground-Fault Protection RECEPTACLE WHITE 120 V 15 A l FAULT BLACK GREEN TOASTER FIGURE 2 As an example, in the toaster circuit above, the black or hot wire is shorted to the metal casing of the toaster. When the circuit closes, all or part of the current is channeled through the toaster frame and then through the green ground wire. When sufficient current flows (typically 6 x 15 A = 90 A), the circuit breaker will open. A protection relay could be installed to detect currents as low as 10 mA, which would open the circuit breaker at a significantly lower level, hence, much quicker than the traditional circuit breaker. Although the example above shows a solidly grounded single-phase circuit, the philosophy is the same on threephase circuits discussed later. Relays and monitors are specifically designed to look for the leading initiators shown in Table 1 by detecting low-level changes in current, voltage, resistance or temperature. DC Systems Direct current (DC) systems have positive and negative buses. If either bus is intentionally grounded, then it is referred to as a grounded system. If neither bus is grounded, then it is referred to as an ungrounded DC system. A ground fault on a DC system may cause damage to the source as well as in the field. If the system is ungrounded, then it is possible to use a ground-fault relay by installing a ground-reference module between the two buses to establish a neutral point (see Figure 3). The ground-fault relay uses this neutral point as a reference to detect low-level ground faults. GROUND REFERENCE MODULE L1 L2 FIGURE 3 Ungrounded AC Systems Ungrounded AC systems, as shown in Figure 4, were used where continuity of power was critical. For example, chemical plants or refineries involving processes that cannot be interrupted without extensive dollar or product loss may have an ungrounded system. However, experience has proven that these systems are problematic and are being replaced with resistance grounded systems. Two major problems with ungrounded systems are transient overvoltages and difficulty locating ground faults. PHASE C DISTRIBUTED SYSTEM CAPACITANCE PHASE A PHASE B FIGURE 4 g An ungrounded system has no point in the system that is intentionally grounded (other than the normal bonding which is always present to connect the non-current-carrying metal parts to ground). Grounding occurs only through system capacitance to ground (as shown in Figure 4). g Continuity of operation occurs because the system can operate with one phase faulted to ground. g An intermittent or arcing fault can produce high transient overvoltages to ground. These voltages are impressed on the phase conductors throughout the system until the insulation at the weakest point breaks down. This breakdown can occur at any point in the electrical system, causing a phase-to-ground-to-phase fault. g Although a ground fault can be detected or alarmed on the system, it is difficult to determine the location of the fault. There are two methods used to detect ground faults on ungrounded systems. One method is to monitor the voltages between the phases and ground. As a ground fault develops, the faulted phase will collapse to ground potential, causing an indicator light to dim. The indicator lights on the unfaulted phases become brighter. A second method to detect a ground fault is to measure the insulation resistance. As the insulation deteriorates, a relay continuously monitoring the insulation resistance can alarm at different levels for predictive maintenance. A visual indicator or meter can also be used. PROTECTION OVERVIEW 15 Overview Littelfuse.com/relayscontrols 516 © 2022 Littelfuse, Inc. Ground-Fault Protection Solidly Grounded Systems Due to the problem of ungrounded systems, a shift in philosophy occurred and designs moved from ungrounded to grounded systems. In most cases, the type of grounding system chosen was solidly grounded. A solidly grounded system is a system of conductors in which at least one conductor or point is intentionally grounded (usually the neutral point of transformer or generator windings). The problem with the direct connection is that ground-fault current can be excessive, causing Arc-Flash hazards, extensive equipment damage, and possible injury to personnel. A solidly grounded system cannot continue to operate with a ground fault. NEUTRAL PHASE C PHASE A PHASE B GROUND FIGURE 5 g In a solidly grounded system, the wye point (or neutral) of the power source is connected solidly to ground and offers a very stable system that maintains a fixed phase-to-ground voltage. g The high ground-fault current is easy to detect with fuses, circuit breakers, or protection relays, allowing for selective tripping (tripping the faulted feeder and not the main feeder). g When a ground fault occurs, high point-of-fault damage can quickly result since the energy available to the ground fault is only limited by the system impedance (which is typically very low). g Due to excessive ground-fault current and Arc-Flash Hazards, the faulted feeder must be removed from service. This does not allow for continuous operation during a ground fault. Figure 6 illustrates an example of the dangers associated with solidly grounded systems. In this example, a ground fault occurs and the overcurrent protection is set at 600 A. ARCING FAULT EQUIPMENT FRAME OR BARE COPPER 600 A / 3 P FIGURE 6 Assume that this ground-fault is not a bolted fault, but an arcing fault due to an insulation breakdown or a partial reduction of clearances between the line and ground. g Because of the arc resistance, fault current may be as low as 38% of the bolted-fault level. This can be in the range of a normal load or a slight overload. g The fault current may be low enough that the overcurrent device (600-A circuit breaker) does not sense a fault, or may pick it up but not trip for a long time. g The energy being supplied by the source is concentrated at the arc and could cause severe equipment damage very quickly. This energy release could cause a fire that in turn, could damage the premises and present an extreme hazard to personnel. Aside from converting this solidly grounded system to resistance grounding, the best way to prevent damage is to detect low-level ground leakage prior to it becoming a ground fault. In order to accomplish this, the protection relay must be able to sense a low-level ground leakage without nuisance tripping. In modern facilities, equipment often generates noise or harmonics that can interfere with a protection relay’s ability to function properly. For example, the noise or harmonics may be higher than the desired ground-fault relay settings, causing the relay to falsely operate when there is no fault on the system. The protection relay must be able to filter out noise or harmonics to provide reliable protection. Resistance-Grounded Systems Resistance grounding solves the problems commonly associated with both ungrounded systems and solidly grounded systems. The name is derived from the addition of a resistor between the system neutral and ground (as shown in Figure 7). The specifications of the resistor are userdetermined to achieve a desired ground-fault current, which must be greater than the system capacitive charging current (explained later in this section). NEUTRAL GROUND PHASE C PHASE A PHASE B FIGURE 7 PROTECTION OVERVIEW 15 © 2022 Littelfuse, Inc. 517 Littelfuse.com/relayscontrols Overview Ground-Fault Protection g Transient overvoltages can be eliminated by correctly sizing the neutral-grounding resistor (NGR) to provide an adequate discharge path for the system capacitance. g Continuity of operation with one ground fault is typically allowable when ground-fault current is <− 10 A. g The NGR limits the available ground-fault current. This eliminates or minimizes point-of-fault damage (Arc-Flash Hazards) and controls the ground-fault voltage. g Pulsing current can be used to locate ground faults when ground-fault current is <−10 A. Pulsing current is created by using a shorting contactor to short out half of the resistance, causing the ground-fault current to double (usually one cycle per second). A hand-held zero-sequence meter is used to detect the fluctuating ground-fault current, and locate the ground fault. g The only disadvantage of resistance grounding is that if the resistor fails, the system will become ungrounded. Resistor monitoring is recommended to protect against this. A protection relay for resistance-grounded systems is used to detect a ground fault and to monitor the neutral-to-ground connection. It can be used to provide alarms or to trip the feeder from service upon the detection of a ground fault. The relay can provide a pulsing circuit that can be used to locate the ground fault. The relay can also alarm or trip if the neutral-to-ground path fails. For systems 5 kV and less, highresistance grounding can be used. High-resistance grounding typically limits the resistor current to 10 A or less. By doing so, the ground fault can remain on the system, given that the system is rated for the voltage shift. For systems above 5 kV, neutral-grounding resistors are typically rated for 25 A or more, and ground-fault current is cleared within 10 s. System Capacitive Charging Current Although not physically connected to ground, electrical conductors and the windings of all components are capacitively connected to ground. Consequently, a small current will flow to ground from each phase. This current does not occur at any particular location; rather, it is distributed throughout the system just as the capacitance to ground is distributed throughout the system. For analysis, it is convenient to consider the distributed capacitance as lumped capacitance, as shown in Figures 5, 6, 7, and 8. lC xC IA + IB + IC = 0 xC xC lA lB A FIGURE 8 Even if the distributed capacitance is not balanced, the ammeter will read zero because all the current flowing through the CT window must return through the CT window. System charging current is the current that will flow into the grounding connection when one phase of an ungrounded system is faulted to ground (see Figure 9). It can be measured as shown below if appropriate precautions are taken: g If the fault occurs on the supply side of the CT, the sum of the currents in the CT window is not zero. g Ammeter A will read the sum of the capacitive currents in the unfaulted phases. This value is the charging current of all the equipment on the load side of the CT. lC xC IA + IB + IC = 0 xC xC lA lB A x FIGURE 9 A single-line diagram of a three-feeder, resistance-grounded system with a fault on feeder 3 is shown in Figure 10. g A CT (A1 and A2) on unfaulted feeders will detect the charging current of that feeder. g A CT (A3) on a faulted feeder will detect the sum of the resistor current (IR) and the charging currents (I1 +I2 ) of the unfaulted feeders. A1 A2 A3 1 2 3 l 1 l 2 l R FIGURE 10 PROTECTION OVERVIEW 15 Overview Littelfuse.com/relayscontrols 518 © 2022 Littelfuse, Inc. Selective coordination in a resistance-grounded system can be achieved if the pick-up setting of each ground-fault relay is greater than the charging current of the feeder it is protecting. If the pick-up setting of a ground-fault relay is less than the charging current of the feeder it is protecting, it will trip when a ground fault occurs elsewhere in the system. This is known as sympathetic tripping.Sympathetic tripping can be avoided by choosing a relay pickup setting larger than the charging current from the largest feeder. If the relative size of the feeders can change, or if the advantage of using one operating value for all ground-fault relays in a system is recognized, then it is prudent to select a pick-up setting for all ground-fault relays that is larger than the system charging current. In order to eliminate transient overvoltages associated with an ungrounded system, it is necessary to use a grounding resistor with a let-through current equal to or larger than the system charging current. What is the minimum acceptable NGR current? Select a pickup setting for the ground-fault relays that exceeds the largest feeder charging current and multiply the operating value by an acceptable tripping ratio. Use the greater of this value or system charging current and select the next-largest available standard let-through current rating. Resistor Monitors As discussed in the resistance-grounded systems section, a failure in the neutral-to-ground path will lead to a dangerous situation. Some examples of failure are stolen wires, loose connections, corrosion, and broken resistor elements. The resistor monitor continuously monitors the path from system neutral to ground for a problem. When a problem occurs, the monitor provides an alarm. Ground-Continuity Monitors Ground-check monitors are used to detect problems in equipment ground conductors. The cable powering mobile equipment typically has an extra wire, or pilot wire, routed with the phase conductors. A monitor uses this pilot wire to send a signal to a terminating device in the equipment, where the signal is sent back on the cable ground conductor to the monitor. The monitor continuously monitors this loop for open or short circuits, indicating that a problem has occurred. The monitor provides an alarm for this condition. As an example, portable loads are grounded via single or multiple conductors in a trailing cable. A ground fault on a portable load will cause fault current to flow through the ground conductors and all other ground-return paths. A hazardous touch voltage can develop when the ground conductor opens and a ground fault develops, assuming there is not enough current to trip a ground-fault relay. If the portable equipment has rubber tires or is not in good contact with earth, then a person who touches the equipment under fault conditions will become part of the ground-return path. Motor Protection Overview Motors are a significant investment and often run critical processes. Motor protection relays are used to protect the windings from damage due to electrical faults and thermal overloads. Adequate motor protection not only prevents motor damage, but also ensures optimal process efficiency and minimal interruption. Cost recovery for protection is achieved by extending the life of the motor, preventing motor rewinds and reducing downtime. Common Motor Problems Overload and Overtemperature Insulation breakdown is a common reason for motor failure. Windings in the motor are insulated with organic materials including epoxy and paper. Insulation degradation occurs when winding temperature exceeds its rating. The National Electrical Manufacturers Association (NEMA) states that the time-to-failure of organic insulation is halved for each 8 to 10°C rise above the motor insulation-class rating. This point is illustrated in Figure 11. Solution: An I2 t Thermal Model provides thermal-overload protection of motor windings during all phases of operation. By integrating the square of the current over time, a thermal model can predict motor temperature and react much quicker than embedded temperature devices. A thermal model takes into consideration the motor service factor, full-load current and class. A dynamic thermal model adjusts the time-to-trip depending on how much motor thermal capacity has been used. Figure 12 illustrates the adjustment in trip time for different current levels at different levels of used thermal capacity (I2 t). A dynamic thermal model allows accurate protection of a motor and allows operations to get the maximum work out of a motor without sacrificing available life. If the motor is hot (high % used thermal capacity) it will trip more rapidly during an overload than if the motor is cold (0% used thermal capacity). In the event of a stall condition, when available motor torque is lower than the torque required by the load, the motor can be de-energized before it overheats. Many old-technology electronic thermal overloads do not take into consideration the values of load current below the full-load current (FLA) pick-up value. Modern overload relays should model currents above and below the FLA pick-up current to achieve maximum output of the motor and maximum life of insulation. On larger induction motors, blockage or loss of ventilation can cause motor hot spots that current-based protection cannot detect without the use of temperature sensors. Resistance temperature detectors (RTDs) are inexpensive devices installed between the stator windings during manufacturing and may be included on motor-end bearings. Motor Protection PROTECTION OVERVIEW 15 © 2022 Littelfuse, Inc. 519 Littelfuse.com/relayscontrols Overview An RTD has a linear change in resistance over its rated temperature range. Using information from an RTD, motorprotection relays can provide protection for loss-of-ventilation, loss-of-cooling, or high-ambient-temperature. The RTD temperature reading can also be used as an input to the thermal model to improve protection. When hotmotor compensation is enabled, the maximum stator-RTD temperature is used to bias the thermal model by increasing used I2 t when the RTD temperature is greater than the thermal-model temperature. Overcurrent, Jam and Undercurrent Overcurrent faults, also referred to as short circuits, can cause catastrophic motor failures and fires. Overcurrents can be caused by phase-to-phase, phase-to-ground, and phase-toground-to-phase faults. A mechanical jam, such as a failed bearing or load, can cause stalling and locked-rotor current to be drawn by the motor, resulting in overheating. Undercurrent protection is loss-of-load protection and is required by some codes as a safety measure. A water pump that cavitates can be dangerous. The water typically provides pump cooling. Without the cooling water, case temperature can reach an extremely high value. If valves are opened under these conditions and cold water is allowed to reach red-hot metal parts, the resulting steam pressures can destroy the pump and pose a serious personnel hazard. Solution: A multifunction motor protection relay has multiple trip and alarm settings for current protection. Overcurrent protection is typically set above locked rotor current and has a minimal delay time. Overcurrent protection may be used to trip a breaker instead of a starter due to the high fault levels. Jam protection is set below overcurrent and has a slightly longer delay time. Jam protection prevents motor heating that would otherwise lead to an overload trip. Jam protection is enabled after the motor is running to avoid tripping on starting current. Undercurrent is set below full-load current to detect loss of load. Under and Overvoltage Overvoltages cause insulation stress and premature breakdown. Undervoltages, such as those caused by brownouts, can lead to increased motor heating. Torque developed by an electric motor changes as the square of the applied voltage. A 10% reduction in voltage results in a 19% reduction in torque. If the motor load is not reduced, the motor will be overloaded. Solution: Under and overvoltage protection are features found in higher-end motor protection relays. Voltage protection can be used pro-actively to inhibit a start. Ground Faults Ground faults are the most common fault and can lead to more serious problems. Ground-fault protection, described elsewhere in this text, is an important consideration in motor loads. Solution: The motor protection relay should be able to detect low-level ground-fault current when used on a resistance-grounded system. HOTTEST TEMPERATURE (°C) CLASS F 100,000 1 50,000 10,000 — 10 — 7 — 5 — 1 — 2 — 5 — 1 — 20 — 10 — 5 — 3 — 2 — 1 5000 1000 500 100 100 110 120 130 140 150 160 180 200 220 240 260 280 300 50 10 5 AVERAGE MOTOR LIFE (HOURS) (YEARS) (MONTHS) (DAYS) FIGURE 11 MOTOR CURRENT (%FLA) 0 100 200 300 400 500 600 700 800 900 1000 ) SDNOCES( PI RT- OT- E IMT 1 2 3 4 5 6 8 10 20 30 40 50 60 80 100 200 300 400 500 600 800 1000 2000 3000 4000 5000 6000 8000 10000 1100 1200 1300 1400 1500 0.1 0.2 0.3 0.4 0.5 0.6 0.8 SHOWN AT 1.15 SERVICE FACTOR 1.00 TO 1.25 2 TIME-TO-TRIP DECREASES AS USED I t INCREASES 0% USED I t (cold) 2 25% USED I t 2 75% USED I t 2 50% USED I t 2 FIGURE 12 Motor Protection PROTECTION OVERVIEW 15 Overview Littelfuse.com/relayscontrols 520 © 2022 Littelfuse, Inc. High-Resistance Winding Faults Winding-to-winding and winding-to-ground failures inside the motor are difficult to detect using the phase and ground-fault CTs due to low magnitudes of current. Solution: Differential protection in high-end motor protection relays use multiple CTs to compare the current entering and leaving the winding. If there is a difference in currents then leakage is occurring. This sensitive protection is used on very large or critical motors. Current and Voltage Imbalance, Phase Loss, Phase Reverse Older motor protection devices did not consider current imbalance and today it is often overlooked. Imbalance increases negative-sequence current which causes additional rotor heating. Phase loss is also referred to as single phasing. When a phase loss occurs, negative-sequence current is equal to the positive-sequence current and imbalance is 100%. In this condition, one motor winding attempts to do the work of three, inevitably leading to overheating. Phase reversal causes the negative-sequence current and voltage to be greater than the positive-sequence current and voltage. Voltage-based protection is advantageous to prevent a start with incorrect sequence. In some applications attempting to spin the motor backwards will result in damage to the load. An example of this is certain impeller designs in downhole pumps. Solution: Modern motor protection relays use digital signal analysis to measure true-sequence components. These sequence components are used for thermal model calculations and take the extra heating into consideration. Voltage imbalance which drives current imbalance can be used as a start inhibit. Sequence components are also used for calculating imbalance, phase loss and phase reversal. Motor Jogging NEMA-designed motors are rated for two starts from cold and one start from hot per hour. Motor jogging refers to excessive starts and can cause overheating. The motor may not get up to full speed and the forced air cooling is not effective. Solution: Since the thermal model accurately tracks the motor’s used thermal capacity at all times, including during starts and between starts, the starts-per-hour feature may not be required. It is included for compatibility with protection relays that do not have dynamic thermal-modeling capability. Motor Protection and the NEC The NEC® requires the motor to be protected by overload devices against excessive heating due to overload and failure to start (Article 430 Section III). Article 430, Section IV also specifies the use of devices to protect against overcurrents such as short circuits and grounds. Both of these NEC® requirements and many additional functions can be met with the use of a multifunction motor protection relay. Article 430.32 (A)(4) requires the use of a protection device having embedded temperature detectors that cause current to the motor to be interrupted when the motor attains a temperature rise greater than marked on the nameplate in an ambient temperature of 40°C for motors larger than 1500 hp. The NEC defines minimum requirements and is intended to provide protection from fire. Protection relays can provide many enhancements above simple fire protection. Communications Network communications can be added to a motor protection relay to allow remote metering of currents, voltages and temperatures. Data logging is a useful feature for troubleshooting and comparing event sequences with process stages. Analysis of information can often show operational issues. Arc-Flash Protection The Consequences of Arc Flash Arcing and arc flashes are uncontrolled, intense, luminous discharges of electrical energy that occur when electric current flows across what is normally an insulating medium. The most common cause of arc faults is insulation failure. These failures may be caused by defective or aging insulation material, poor or incorrect maintenance, dust, moisture, vermin, and human error (touching a test probe to the wrong surface or a tool slipping and touching live conductors). Arc-Flash events are dangerous, and potentially fatal, to personnel. According to OSHA, industrial Arc-Flash events cause about 80% of electrically-related accidents and fatalities among qualified electrical workers. Even if personnel injuries are avoided, Arc Flash can destroy equipment, resulting in costly replacement and downtime. Arc-Flash Safety Standards NFPA 70E, Handbook for Electrical Safety in the Workplace. outlines the practices and standards that companies should follow to protect workers and equipment from Arc Flash and other electrical hazards. It specifies practices designed to make sure that an electrically safe work condition exists. In Canada, CSA Z462, Workplace electrical safety, specifies safe workplace practices. There are also various provincial regulations pertaining to electrical safety. The NFPA 70E and the CSA Z462 hold both employers and their employees responsible for creating a workplace for electrical workers that is not just safe but puts in place the best possible processes and procedures that are fully understood, practiced and enforced for optimal results. Using Arc-Flash relays is one way to protect the functional reliability of the distribution board and at the same time comply with the requirements of NFPA 70E and CSA Z462. Arc-Flash Protection PROTECTION OVERVIEW 15 © 2022 Littelfuse, Inc. 521 Littelfuse.com/relayscontrols Overview Arc-Flash Protection Arc-Flash Mitigation NFPA 70E goes into great detail on procedures to avoid electrical shock and Arc-Flash events. Sometimes, though, it’s necessary to work on live circuits. For these cases, NPFA 70E specifies approach distances and use of personal protection equipment (PPE). Current limiting fuses or current-limiting circuit breakers help protect against arc flashes. They allow only a certain amount of energy to pass before they open a circuit. Because an Arc Flash can draw a fraction of bolted-fault current, circuit breakers cannot be relied upon to distinguish between the arcing current and a typical inrush current. High-resistance grounding (HRG) is another technique for protecting against arc flashes. If a phase faults to ground, then the resistance limits current to just a few amps; not enough to cause downtime by tripping the overcurrent protection device, and not enough to allow an Arc Flash. It is important to remember that while resistance grounding prevents Arc Flash from phase-toground shorts, it has no effect on phase-to-phase shorts. Another way to mitigate the dangers of arc flashing is by redesigning the switchgear. Switchgear cabinets can be designed to contain and channel energy away from personnel during an Arc Flash. Arc-Flash relays Arc-Flash relays are microprocessor-based devices that use optical sensors to detect the onset of a flash. The sensors are strategically placed in various cubicles or drawers inside the switchboard. Installing an Arc-Flash relay to rapidly detect developing arc flashes greatly reduces the total clearing time and the amount of energy released through an arcing fault. In turn, there is less damage to equipment and fewer and less severe injuries to nearby personnel. Arc-Flash Relay Selection Criteria When selecting an Arc-Flash relay, there are six important criteria: 1. Reaction time 2. Trip reliability 3. Avoidance of nuisance tripping 4. Sensor design and installation 5. Ease of use Reaction Time Since light is the earliest detectable indication that an Arc Flash is occurring, Arc-Flash relays use optical light sensors to detect the arc that is forming. The output of the light sensor is hard-wired to the Arc-Flash relay, which trips a circuit that interrupts the energy supply in the Arc. The response time of an Arc-Flash relay is approximately 1-5 ms at light intensities of about 10,000 lux or higher. Within that time frame, the optical sensor output can actuate a switch or circuit breaker to cut off current feeding the arc. The overall current clearing time depends on the protection strategy used and the performance of the external switch or circuit breaker used. The breaker will typically take an additional 35-50 ms to open, depending on the type of breaker and how well it is maintained. The electronic output to turn on is a function of the type of output relay used. Solid-state outputs (for example, insulated gate bipolar transistors (IGBTs)) are much faster than electromechanical relays and can operate within 200 microseconds. Trip Reliability Reliable tripping is the most important characteristic of an ArcFlash relay, because this ensures mitigation of an arcing fault. Two aspects of reliability should be considered: trip redundancy and system-health monitoring. Redundant Tripping. Arc-Flash relays should offer a redundant tripping feature, which means it has both primary and secondary trip path logic. The primary path is controlled by the internal microprocessor and its embedded software, and works by activating the coil of the primary trip relay. The redundant path typically uses a discrete solid-state device that does not go through the microprocessor. Any failure in the primary (microprocessor) path will cause the unit to automatically switch to its redundant path, which activates a shunt-trip relay without delay when a sensor input is above the light detection threshold. An often overlooked advantage of a solid-state trip path compared to a microprocessor-based circuit is the reaction time when the relay is first powered up. Wiring mistakes, tools left in hazardous locations, and the regular stresses of powering up all contribute to the risk of an Arc Flash on power up. A microprocessor can require 200 ms or more before it is able to start scanning the optical sensors. However, a solid-state trip path can detect an Arc and send a trip signal in as little as 2 ms. In addition, there are fail- safe features that alert operators when, for example, the microprocessor fails. Health monitoring. Health monitoring makes sure the system is in good operating condition and should extend from the light sensors to the output of the Arc-Flash relay trip circuitry. Health monitoring starts on the sensors. A signal is sent from the relay to the light sensors, where a test light is detected by the sensor and sent back to the relay. In the case of a fiber-optic sensor, this also verifies the entire length of the fiber is not pinched or broken. On-sensor health indication is critical in preventing maintenance work on equipment where protection is not working. It also has the added benefit of providing rapid fault location. Following the path of a trip signal from the sensor, internal monitoring must also include the primary and redundant trip circuit. Low voltage across the IGBT indicates a wiring fault or an error in the trip coil, and a high voltage is a sign of an error in the IGBT switch, both of which are also reported and logged. The IGBT is also thermally protected against overloads, and will turn off if it overheats. However, the thermal protection has a 100 ms delay before acting, meaning that even a dangerously overheated coil will attempt to signal a trip before resuming thermal protection. PROTECTION OVERVIEW 15 Overview Littelfuse.com/relayscontrols 522 © 2022 Littelfuse, Inc. CT Application III. CT APPLICATION Current Transformers (CTs) A current transformer is defined as a transformer that produces a current in its secondary circuit that is in proportion to current in its primary circuit. Although there are other types of CTs, only the window (or ring) type will be discussed here. Window-type CTs get their name from their design that consists of a ring-shaped core. This core is formed by a single length of strip ferromagnetic material tightly wound to form the ring-shaped core. A CT operates on a principle of flux balance, as shown in Figure 1. If the primary winding is energized with the secondary circuit open-circuited, the transformer becomes an iron-cored inductor. The primary current generates a magnetic flux in the core as shown (flux direction can be determined by the right-hand rule). When the secondary winding is connected to a burden or is short circuited, current flows through the secondary winding creating magnetic flux in the core in opposition to the magnetizing flux created by the primary current. If losses are ignored, the secondary flux balances exactly to the primary flux. This phenomenon is known as Lenz’s Law. SECONDARY FLUX SECONDARY WINDING PRIMARY WINDING T2 T1 PRIMARY FLUX FIGURE 1 Lead Length The secondary lead resistance of CTs cannot be ignored, particularly with low Volt-Amperes (VA) CTs. For example, let’s look at an electronic overload relay. The relay’s CT input impedance or burden (ZB) = 0.01 Ω The maximum current (I) = 10 A The CT rating (P) = 5 VA Now let’s solve for the maximum length of #14 AWG leads that will result in a rated accuracy for a 10 A secondary current. Solving for maximum total impedance (ZT ): P = I²ZT ZT = P / I² = 5 / 10² = 0.05 Ω Avoidance of Nuisance Tripping A typical Arc-Flash Relay system has an integrated three-phase current measurement function that detects and reacts to short circuit and overcurrent conditions. Although this is not a requirement for the system to operate, this option will increase the reliability of the system (minimize unwanted tripping). If the microprocessor logic receives an input from a light sensor, it checks for a rapidly rising input from the current transformers. Two conditions need to be fulfilled before the trip is sent to the circuit breaker: a certain current flow that exceeds the normal operating current of the system (the threshold level is adjustable from 10-1000% of the full load current) and a signal from the arc-flash sensor, implying that the sensor has reacted to a highintensity light source. Sensor Design and Installation Arc-Flash relay installations utilize multiple fixed-point light sensors near vertical and horizontal bus bars where arcing faults are apt to occur in feeder switchgear cabinets. Sufficient numbers of sensors should be installed to cover all accessible areas, even if policy is to only work on de-energized systems. At least one sensor should have visibility to an arc fault if a person blocks another sensor’s field of view. Light sensors may also be installed in other electrical cabinets and on panels that are subject to routine maintenance and repairs. A fiber-optic sensor, which have a 360° field of view for detecting light, allows more flexible positioning of the light sensing locations, as the fiber-optic strands can be looped throughout an enclosure or panel to cover challenging component layouts. Easy to Use Hardware and Software Another important factor to consider is ease of use. Some relays may require field assembly, calibration, or advanced configuration before installing. It is critical to consider those extra steps and the capabilities of the operators who will be using the devices. Often, very complicated devices can be misused because of incorrect setup or configuration, which can defeat the purpose of the device altogether. A few Arc-Flash Relays have software that provides event logging. To make troubleshooting easier, this software should record the specific sensor that initiated the fault in the data records. PGA-LS10 (Point Sensor) PGA-LS20/ PGA-LS25 (Fiber-Optic Sensor) 24 Vdc Battery Backup (Optional) (Recommended) (Arc-Flash Protection Relay) PGR-8800 CTs 5-A-SECONDARY PHASE CT’s L2 L1 A B C Examples of Arc-Flash Relay light sensor installation in switchgear. PROTECTION OVERVIEW 15 © 2022 Littelfuse, Inc. 523 Littelfuse.com/relayscontrols Overview IV. RESISTANCE-GROUNDING CONVERSION Convert Ungrounded to Resistance-Grounded Systems Resistance grounding protects a system against transient overvoltages caused by intermittent ground faults and it provides a method to locate ground faults. (Transient overvoltages and inability to locate ground faults are the most common safety issues with ungrounded systems.) Conversion of delta-connected or wye-connected sources with inaccessible neutrals require a zigzag transformer to derive an accessible neutral for connection to a neutral grounding resistor (NGR). The neutral is only used for the NGR and not for distribution. During normal operation the only current that flows in the zigzag transformer is an extremely small magnetizing current. When one phase is grounded, the NGR and the zigzag transformer provide a path for ground-fault current to flow. Figure 1 Design Note 1: A zigzag conversion requires a three-phase connection to the existing power system, typically at the main transformer or switchgear. See Figure 1. Design Note 2: The resistor let-through current must be greater than the system capacitive charging current (see Section I). Design Note 3: Protection, coordination, and annunciation systems depend on the integrity of the NGR. NGR monitoring with an SE-330 or SE-325 is recommended. Converting to a Resistance-Grounded System Solving for the maximum lead resistance (Z W): ZT = Z W+Z B Z W= 0.05-0.01 = 0.04 Ω If we look up the #14 AWG resistance we find it equals 2.6 ohms/1000 ft Therefore, lead length = Z W / #14 AWG resistance Maximum lead length= (0.04 x 1000) / 2.6 = 15.4 ft CT Installation A CT should not be operated with its secondary opencircuited. If the secondary is opened when primary current is flowing, the secondary current will attempt to continue to flow so as to maintain the flux balance. As the secondary circuit impedance increases from a low value to a high value the voltage across the secondary winding will rise to the voltage required to maintain current flow. If the secondary voltage reaches the breakdown voltage of the secondary winding, the insulation will fail and the CT will be damaged. Furthermore, this situation presents a personnel shock hazard. When a ring-type CT is used to monitor a single conductor or multiple conductors, the conductors should be centered in the CT window, as shown below in Figure 2, and should be perpendicular to the CT opening. In some applications it is difficult or impossible to install the primary conductor through the CT window (example: existing bus bar structure). For these applications a split core CT is sometimes used. Performance of split core CTs may be less than that of solid core CTs. A A B B C C A B C SPACER Incorrect Correct FIGURE 2 CT characteristics are normally specified at a single frequency such as 50 or 60 Hz. Therefore the question arises: What happens when CTs are used with variable frequency drives (VFDs)? For CTs that are linear to approximately 10x rated primary current at 60 Hz, the Volts/Hertz ratio is approximately constant. That is, for all other conditions held the same at 6 Hz, the CT will be linear to only 1x rated current and at 30 Hz the CT will be linear to 5x rated current. For a standard silicon-steel-core CT, the upper bandwidth frequency is approximately 5 kHz. PROTECTION OVERVIEW 15 Overview Littelfuse.com/relayscontrols 524 © 2022 Littelfuse, Inc. Ungrounded, Solidly Grounded and Resistance-Grounded Systems UNGROUNDED SYSTEM PHASE C DISTRIBUTED SYSTEM CAPACITANCE PHASE A PHASE B NEUTRAL PHASE C PHASE A PHASE B GROUND NEUTRAL GROUND PHASE C PHASE A PHASE B Advantages • Operation possible with one faulted phase Disadvantages • Ground faults are difficult to locate • Transient overvoltages damage equipment SOLIDLY GROUNDED SYSTEM Advantages • Eliminates transient overvoltages • Selective tripping possible Disadvantages • Costly point-of-fault damage • Cannot operate with a ground fault • Ground-fault Arc-Flash hazard • Increased Arc-Flash risk RESISTANCE-GROUNDED SYSTEM Advantages • Reduced point-of-fault damage and Arc-Flash risk • Eliminates transient overvoltages • Simplifies ground-fault location • Continuous operation with a ground fault • Selective tripping possible • No ground-fault Arc-Flash hazard Disadvantages • Failure of the neutral-grounding resistor renders currentsensing ground-fault protection inoperative PROTECTION OVERVIEW 15 © 2022 Littelfuse, Inc. 525 Littelfuse.com/relayscontrols Overview Convert Solidly Grounded to Resistance-Grounded Systems Resistance grounding protects a system against Arc-Flash Hazards caused by ground faults and provides a method for continuous operation or an orderly shutdown procedure. (Ground faults are estimated to be 98% of all electrical faults.) Since the neutral point of the power source is available, the solid connection between neutral and ground is replaced with a grounding resistor. This resistor limits ground fault current to a predetermined value, typically 5 A for 480 V systems (the system capacitive charging current is usually less than 3 A). By limiting the ground-fault current to 5 A or less, there are no Arc-Flash Hazards associated with ground faults. This allows for continuous operation during the first ground fault. During a ground fault on a resistance-grounded (RG) system, a voltage shift occurs (the same shift experienced on ungrounded systems). The faulted phase collapses to ~0 V, the non-faulted phases rise to line-to-line voltage with respect to ground, and the neutral point rises to line-to-neutral voltage with respect to ground. Figure 2 Design Note 1: An NGR conversion for a solidly grounded system requires a neutral connection to the existing power system, typically at the main transformer or switchgear. See Figure 2. Design Note 2: The voltage shift requires equipment to be fully rated at line-to-line voltage with respect to ground. This may require TVSSs, VFDs, meters, etc. to be reconfigured or replaced. Design Note 3: The voltage shift also restricts neutral distribution. The neutral typically cannot be distributed due to its potential rise during ground faults. Single-phase line-to-neutralvoltage loads must be served by a 1:1 isolation transformer or converted to line-to-line loads. Design Note 4: The resistor let-through current must be greater than the system capacitive charging current (see Section I). Design Note 5: Protection, coordination, and annunciation systems depend on the integrity of the NGR. Monitoring with an SE-330 or SE-325 NGR Monitor is recommended. Ungrounded, Solidly Grounded and Resistance-Grounded Systems PROTECTION OVERVIEW 15 Overview Littelfuse.com/relayscontrols 526 © 2022 Littelfuse, Inc. IEEE DEVICE NUMBERS 1 - Master Element 2 - Time Delay Starting or Closing Relay 3 - Checking or Interlocking Relay 4 - Master Contactor 5 - Stopping Device 6 - Starting Circuit Breaker 7 - Rate of Change Relay 8 - Control Power Disconnecting Device 9 - Reversing Device 10 - Unit Sequence Switch 11 - Multi-function Device 12 - Overspeed Device 13 - Synchronous-speed Device 14 - Underspeed Device 15 - Speed - or Frequency, Matching Device 16 - Data Communications Device 17 - Shunting or Discharge Switch 18 - Accelerating or Decelerating Device 19 - Starting to Running Transition Contactor 20 - Electrically Operated Valve 21 - Distance Relay 22 - Equalizer Circuit Breaker 23 - Temperature Control Device 24 - Volts Per Hertz Relay 25 - Synchronizing or Synchronism-Check Device 26 - Apparatus Thermal Device 27 - Undervoltage Relay 28 - Flame Detector 29 - Isolating Contactor or Switch 30 - Annunciator Relay 31 - Separate Excitation Device 32 - Directional Power Relay 33 - Position Switch 34 - Master Sequence Device 35 - Brush-Operating or Slip-Ring Short-Circuiting Device 36 - Polarity or Polarizing Voltage Devices 37 - Undercurrent or Underpower Relay 38 - Bearing Protective Device 39 - Mechanical Condition Monitor 40 - Field (over/under excitation) Relay 41 - Field Circuit Breaker 42 - Running Circuit Breaker 43 - Manual Transfer or Selector Device 44 - Unit Sequence Starting Relay 45 - Abnormal Atmospheric Condition Monitor 46 - Reverse-phase or Phase-Balance Current Relay 47 - Phase-Sequence or Phase-Balance Voltage Relay 48 - Incomplete Sequence Relay 49 - Machine or Transformer, Thermal Relay 50 - Instantaneous Overcurrent Relay 51 - AC Inverse Time Overcurrent Relay 52 - AC Circuit Breaker 53 - Exciter or DC Generator Relay 54 - Turning Gear Engaging Device 55 - Power Factor Relay 56 - Field Application Relay 57 - Short-Circuiting or Grounding (Earthing) Device 58 - Rectification Failure Relay 59 - Overvoltage Relay 60 - Voltage or Current Balance Relay 61 - Density Switch or Sensor 62 - Time-Delay Stopping or Opening Relay 63 - Pressure Switch 64 - Ground (Earth) Detector Relay 65 - Governor 66 - Notching or Jogging Device 67 - AC Directional Overcurrent Relay 68 - Blocking or “Out-of-Step” Relay 69 - Permissive Control Device 70 - Rheostat 71 - Liquid Level Switch 72 - DC Circuit Breaker 73 - Load-Resistor Contactor 74 - Alarm Relay 75 - Position Changing Mechanism 76 - DC Overcurrent Relay 77 - Telemetering Device 78 - Phase-Angle Measuring Relay 79 - AC Reclosing Relay 80 - Flow Switch 81 - Frequency Relay 82 - DC Reclosing Relay 83 - Automatic Selective Control or Transfer Relay 84 - Operating Mechanism 85 - Communications, Carrier or Pilot-Wire Relay 86 - Lockout Relay 87 - Differential Protective Relay 88 - Auxiliary Motor or Motor Generator 89 - Line Switch 90 - Regulating Device 91 - Voltage Directional Relay 92 - Voltage and Power Directional Relay 93 - Field Changing Contactor 94 - Tripping or Trip-Free Relay ANSI DEVICE NUMBERS AFD - Arc Flash Detector CLK - Clock or Timing Source DDR - Dynamic Disturbance Recorder DFR - Digital Fault Recorder ENV - Environmental Data HIZ - High Impedance Fault Detector HMI - Human Machine Interface HST - Historian LGC - Scheme Logic MET - Substation Metering PDC - Phasor Data Concentrator PMU - Phasor Measurement Unit PQM - Power Quality Monitor RIO - Remote Input/Output Device RTU - Remote Terminal Unit/Data Concentrator SER - Sequence of Events Recorder TCM - Trip Circuit Monitor SOTF - Switch On To Fault TYPICAL SUFFIXES A - Alarm/Auxiliary Power AC - Alternating Current B - Battery/Blower/Bus BT - Bus Tie C - Capacitor/Condenser/Compensator/ Carrier Current/Case/Compressor DC - Direct Current E - Exciter F - Feeder/Field/Filament/ Filter/Fan G - Generator/Ground* M - Motor/Metering N - Network/Neutral* P - Pump/Phase Comparison R - Reactor/Rectifier/Room S - Synchronizing/Secondary/Stainer/Sump/ Suction (Valve) T - Transformer/Thyratron TH - Transformer (High-voltage Side) TL - Transformer (Low-voltage Side) TT - Transformer (Tertiary-voltage Side) U - Unit Note: Descriptions per IEEE Std C37.2-1996 *Suffix N is preferred when the device is connected in the residual of a polyphase circuit, is connected across broken delta, or is internally derived from the polyphase current or voltage quantities. The suffix G is preferred where the measured quantity is in the path of ground or, in the case of ground fault detectors, is the current flowing to ground. IEEE/ANSI Device Numbers and Typical Suffixes PROTECTION OVERVIEW 15 © 2022 Littelfuse, Inc. 527 Littelfuse.com/relayscontrols Appendix Dimensional Drawings DIMENSIONAL DRAWINGS Measurements: inches (millimeters) Figure 1 Figure 3 Figure 2 601; 601-CS-D-P1; 777; 777-ACCUPOWER; 777-KW/HP-P2; 77C; 77C-KW/HP RS485MS-2W; COM 4-20 3.000 [76.2] 2.300 [58.42] 1.00 [25.4] 4.760 [120.904] 2.628 [66.75] 3.750 [95.25] 0.635 [16.129] 0.700 [17.78] 0.350 [8.89] 0.294 [7.47] 0.569 [14.45] 0.680 [17.27] 0.159 [4.038] 0.415 [10.54] 0.274 [6.96] 2.456 [62.38] 2.882 [73.20] 0.830 [21.08] DEPLUGGABLE TERMINAL BLOCKS ® REMOTE RESET ETHERNET 10Base-T MODBUS OVERLOAD COMM. STATUS R R C I1 I2 I3 I4 1 2 3 4 5 CIO-EN ETHERNET Communication and I/O PILOT DUTY RATING 480VA @ 240VAC, B300 5A @ 240VAC GENERAL PURPOSE SCREW TORQUE RATING 0.5 Nm (5 in.-lbs.) DIGITAL INPUTS OUTPUT A OUTPUT B IND. CONT. EQ. LISTED 784X E68520 REV. 00 Series B 3.000 [76.2] inches [millimeters] 3.100 [78.74] 3.850 [97.79] 3.600 [91.44] 2.280 [57.91] 3.050 [77.47] 1.200 [30.48] 3.850 [97.79] 3.600 [91.44] 2.650 [67.31] D. 0.650 [16.51] 0.200 [5.08] OPTIONAL LOOP HOLES A MAIN CONDUCTORPASS HOLES B C inches [millimeters] 4.700 [119.38] 5.050 [128.27] 2.08 [52.83] 2.900 [73.66] 2.16 [54.86] 0.77 [19.56] inches [millimeters] CIO-120-DN-P; CIO-DN-P; CIO-EN; CIO-MB; CIO-120-MB; CIO-777-PR APPENDIX – DIMENSIONAL DRAWINGS 16 Littelfuse.com/relayscontrols 528 © 2022 Littelfuse, Inc. Appendix Dimensional Drawings DIMENSIONAL DRAWINGS Measurements: inches (millimeters) 1.02 5.97 [25.98] [151.51] 6.37 [161.67] 0.99 [25.15] #6 MOUNTING SCREWS PROVIDED PANEL 0.062 - 0.100 THICK [1.574 - 2.54] 3.5 [88.9] 0.75 [19.05] inches [millimeters] Figure 4 Figure 5 RM2000 inches [millimeters] 4.544 [115.417] 3.619 [91.922] 1.425 [36.195] 0.9 [22.86] 0.75 [19.05] 2.5 [63.5] RM1000 APPENDIX – DIMENSIONAL DRAWINGS 16 © 2022 Littelfuse, Inc. 529 Littelfuse.com/relayscontrols Appendix Dimensional Drawings DIMENSIONAL DRAWINGS Measurements: inches (millimeters) BOTTOM 2.375 [60.331] 1.75 [44.45] SIDE 3.15 [80.01] 0.5 [12.7] inches [millimeters] Figure 8 ACBC-120; ALT; ALT-XXX-X-SW; ISS-101; PC-XXX-LLC; 201-100-SLD; 201A; 201A-AU; 201A-9; 201-XXX-SP; 201-XXX-DPDT; 201-XXX-SP-DPDT Figure 6 Figure 7 4.50 114.3 5.27 133.9 2.93 74.4 0.38 9.5 1.47 37.2 inches [millimeters] Max 2.95 [74.9] Typ. 0.15 [3.8] 2.17 Typ. 55 inches [millimeters] 102A; 250A; 350; 355; 455; 50R; 50R-400-ALT; CP5; T10 202; 202-200-SP 1.427 [36.245] 2.663 [67.64] 1.0 [25.4] inches [millimeters] 2.663 [67.64] 0.25 dia. mounting hole for mounting screw 0.25 dia. indentation for anti-rotation screw 1.427 [36.245] 2.663 [67.64] 1.0 [25.4] inches [millimeters] 2.663 [67.64] 0.25 dia. mounting hole for mounting screw 0.25 dia. indentation for anti-rotation screw APPENDIX – DIMENSIONAL DRAWINGS 16 Littelfuse.com/relayscontrols 530 © 2022 Littelfuse, Inc. Appendix Dimensional Drawings DIMENSIONAL DRAWINGS Measurements: inches (millimeters) Figure 9 Figure 10 Figure 11 Informer; Informer-MS AF0100 460; 460-15-100-XXX; 460-XXX-SP; ISS-100; ISS-102; PC-102 5.025in 127.64mm 3.526in 89.56m m 0.203in 5.16mm 3.750in 95.25mm 3.015in 76.58m m 2.356in 59.84m m 1.391in 35.33m m APPENDIX – DIMENSIONAL DRAWINGS 16 © 2022 Littelfuse, Inc. 531 Littelfuse.com/relayscontrols Appendix Dimensional Drawings DIMENSIONAL DRAWINGS Measurements: inches (millimeters) 111P / 233P / 235P DIMENSIONS 4.03" (102.36) 5.25" (133.35) 4.50" (114.30) 0.375" (9.53) 2.90" (73.66) 2.163(54.94111P / 233P / 235P DIMENSIONS 4.03" (102.36) 5.25" (133.35) 4.50" (114.30) 0.375" (9.53) 2.90" (73.66) 2.163" (54.94) 2.913" (73.99) Figure 12 Figure 13 Figure 15 Figure 14 111P; 233P; 233P-1.5; 235P 0.192 [0.488] 3.511 [89.179] 2.350 [59.690] 3.750 [89.18] 0.621 [15.773] 5.025 [127.365] inches [millimeters] ISS-105; PC-105 1.78 45.1 0.72 18.2 2.50 63.4 0.20 5.1 SIDE VIEW 2.25 57.2 1.13 28.6 2.70 68.5 CL TOP VIEW LED STATUS INDICATOR C'BORE FOR #8 SCREW inches [millimeters] LSRX; LSRX-C 3.12 [79.25] 3.56 [90.43] 1.67 [42.42] 1.07 [27.18] 2.30 [58.42] inches [millimeters] 0.725 [18.415] LSR-0; LSR-XXX; LSRU APPENDIX – DIMENSIONAL DRAWINGS 16 Littelfuse.com/relayscontrols 532 © 2022 Littelfuse, Inc. Appendix Dimensional Drawings DIMENSIONAL DRAWINGS Measurements: inches (millimeters) HSPZA22SL TRDU TRU ASQU; ASTU; DSQU; DSTU (snap for mounting bases) ERD3425A; ERDI; ERDM 3.5 (88.9) 2.94 (74.7) 0.8 (20.3) 1.70 (43.2) 0.25 (6.35) 1.94 (49.3) 2.50 (63.5) 0.187 (4.75) ORB; ORM; ORS 0.50 (12.7) 1.50 (38.1) 1.50 (38.1) 2.12 (53.8) 3.69 (93.7) 3.00 (76.2) 0.163 (4.14) 0.25 (6.35) 1.88 (47.8) 0.38 (9.7) CT; ESD52233; ESDR; FS100 (medium power); FS200; FS300; KRD3; KRD9; KRDB; KRDI; KRDM; KRDR; KRDS; KRPD; KRPS; KSD1; KSD2; KSD3; KSDB; KSDR; KSDS; KSDU; KSPD; KSPS; KSPU; KVM; T2D120A15M; TA; TAC1; TDU; TDUB; TDUI; TDUS; TL; TMV8000; TS1; TS2; TS441165; TS6; TSA141300; TSB; TSD1; TSD2; TSD3411S; TSD6; TSD7; TSD94110SB; TSDB; TSDR; TSDS; TSS; TSU2000 HLVA6I23; HRDB; HRDI; HRDM; HRDR; HRDS; HRIS; HRPS; HRV; RS FA; FS; FSU1000*; PHS*; PTHF4900DK*; SIR1; SIR2; SLR1*; TH1; THC; TCR9C; THD1B410.5S; THD2; THD3C42A0; THD7; THDB; THDS; THS PLM; PLR; TDB; TDBH; TDBL; TDI; TDIH; TDIL; TDM; TDMB; TDMH; TDML; TDR; TDS; TDSH; TDSL FS500; PRLM; TRB; TRM; TRS 1.5 (38.1) 0.5 (12.7) 0.94 (23.88) 0.19 (4.83) 1.0 (25.4) “P” clamp (P1023-2) FS100 (low current flasher); FS491 Figure 16 Figure 17 Figure 18 Figure 19 Figure 20 Figure 21 Figure 22 Figure 25 Figure 23 Figure 24 Figure 26 Figure 27 *If unit is rated @ 1A, see Figure 16 APPENDIX – DIMENSIONAL DRAWINGS 16 © 2022 Littelfuse, Inc. 533 Littelfuse.com/relayscontrols Appendix Dimensional Drawings DIMENSIONAL DRAWINGS Measurements: inches (millimeters) Measurements: inches (millimeters) SC3; SC4 2.5 (63.5) 1.94 (49.3) 0.80 (20.32) 0.25 (6.35) 0.187 (4.75) DIA. 3.5 (88.9) 2.94 (74.7) 1.22 (31) WVM 0.25 (6.35) 0.55 (13.97) 5.9 (149.9) 6.9 (175.3) 0.50 (12.7) 3.3 (83.8) 4.4 (111.8) 2.4 (61.0) 0.68 (17.27) 2.2 (55.9) DLMU FB9L; HLMU; SCR9L PLMU11 LLC4; LLC6; PLS TCS; TCSA 2.0 (50.8) 2.0 (50.8) 1.75 (44.5) 0.75 (19.05) 0.25 (6.35) DIA. 0.36 (9.14) DIA. Figure 28 Figure 29 Figure 30 Figure 31 Figure 32 Figure 33 Figure 34 Figure 35 Figure 36 LCS10T12 Figure 37 Figure 38 ECS; ECSW 3.5 (88.9) 0.36 (9.14) 0.187 (4.75) 0.25 (6.35) 2.94 (74.7) 0.80 (20.3) 1.75 (44.5) 1.94 (49.3) 2.5 (63.5) (ECS has spade connectors and ECSW has terminal board) DCSA LPM CURRENT LIMITING RESISTOR 12 ± 1 (304.8 ± 25.4) STRIPPED 0.25 (6.35) 0.53 (13.46) 0.28 (7.11) 0.22 (5.59) UL1007 24 AWG (0.25 mm2 ) <_ APPENDIX – DIMENSIONAL DRAWINGS 16 Littelfuse.com/relayscontrols 534 © 2022 Littelfuse, Inc. Appendix Dimensional Drawings DIMENSIONAL DRAWINGS Measurements: inches (millimeters) KEY MODEL NUMBERS ENDING IN: N C W 0.440” (11.176 mm) 0.250” (6.350 mm) X 3.620” (91.948 mm) 3.500” (88.900 mm) Y 2.120” (53.848 mm) 2.500” (63.500 mm) Z 0.190” (4.826 mm) 0.250” (6.350 mm) TVM; TVW LLC8 LLC2 4.0 (101.6) 0.5 (12.7) 2.0 (50.8) 0.163 (4.14) 3.0 (76.2) 0.44 (11.35) 0.25 (6.35) 3.62 (91.9) 3.5 (88.9) 2.12 (53.8) 2.5 (63.5) 0.19 (4.83) 0.25 (6.35) LLC5 [ ] [ ] [ ] [ ] ARP FB; SCR 0.80 (20.3) 1.75 (44.5) 0.36 (9.1) 3.5 (88.9) 2.94 (74.7) 0.187 (4.75) 0.28 (7.1) 1.94 (49.3) 0.28 (7.1) 2.5 (63.5) PCR Figure 39 Figure 40 Figure 41 Figure 42 Figure 43 Figure 44 Figure 46 Figure 47 1.5 (38.1) 0.94 (23.88) 1.0 (25.4) 0.19 (4.83) 0.5 (12.7) 2.10 (53.3) 0.94 (23.88) 0.5 (12.7) 14AWG 0.065 (1.65) “P” clamp (P1023-2) 1.5 (38.1) 0.94 (23.88) 1.0 (25.4) 0.19 (4.83) 0.5 (12.7) 2.10 (53.3) 0.94 (23.88) 0.5 (12.7) 14AWG 0.065 (1.65) “P” clamp (P1023-2) MSM Figure 45 = Nylon Standoffs 2.08 (52.8) 3.5 (88.9) 0.234 (5.94) 2.0 (50.8) 2.07 (52.6) 0.25 (6.35) 0.50 (12.7) 0.163 (4.14) 2.75 (69.9) 0.285 (7.24) 0.94 (23.9) 0.22 (5.59) LLC1 APPENDIX – DIMENSIONAL DRAWINGS 16 © 2022 Littelfuse, Inc. 535 Littelfuse.com/relayscontrols Appendix Dimensional Drawings DIMENSIONAL DRAWINGS Measurements: inches (millimeters) Figure 48 Time Delay Relay Seconds 1.5 1.0 0.5 00.5 2.0 2.5 3.0 2.31 1.69 3.63 MAX 2.91 1.75 2.38 Time Delay Relay Seconds 1.5 1.0 0.5 00.5 2.0 2.5 3.0 2.31 1.69 3.63 MAX 2.91 1.75 2.38 3.63 MAX 2.91 1.75 2.38 PRS65 SIO-RTD-02-00 Measurements: inches Figure 49 87.0 (3.43) 112.5 (4.43) ADDRESS SWITCH ACCESS COVER CABLE-TIE EYELET 4 LOCATIONS 12.5 (0.50) 60.0 (2.36) 14.5 (0.57) 6.3 (0.25) 100.0 (3.94) 6.3 (0.25) M4 OR 8-32 TAP 52.5 (2.07) 56.0 (2.20) (NOTE 3) NOTES: 1. DIMENSIONS IN MILLIMETERS (INCHES). 2. MOUNTING SCREWS: M4 OR 8-32. 3. OVERALL HEIGHT WHEN MOUNTED ON DIN EN50022 35-mm x 7.5-mm TOP-HAT RAIL. R C D R C D R C D R C D R S P G D C R D C R D C R D C - + + 2 4 V 0 V S H S H S H S H INP1 INP8 INP 2 INP7 PWR COMM INP 3 INP6 INP 4 INP5 COMM SIO-RTD INPUT MODULE 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 34 33 32 31 30 29 28 2726 25 24 23 22 21 20 19 PWR APPENDIX – DIMENSIONAL DRAWINGS 16 Littelfuse.com/relayscontrols 536 © 2022 Littelfuse, Inc. Appendix Dimensional Drawings DIMENSIONAL DRAWINGS Measurements: inches (millimeters) MP8000 Figure 50 4.08 (103.63) 0.63 (16.00) 1.25 (31.75) 4.79 (121.67) 2.93 (74.42) 3.10 (78.74) 2.50 (63.50) 4.08 (103.63) 4.79 (121.67) 2.93 (74.42) 4.08 (103.63) 0.63 (16.00) 1.25 (31.75) 4.79 (121.67) 2.93 (74.42) 3.10 (78.74) 2.50 (63.50) APPENDIX – DIMENSIONAL DRAWINGS 16 © 2022 Littelfuse, Inc. 537 Littelfuse.com/relayscontrols Index ALPHANUMERIC INDEX INDEX 102A Series pg 198 111-Insider-P / 231-Insider-P 101 111P / 233P / 233P-1.5 Series 106 201-100-SLD 136 201-XXX-DPDT Series 204 201-XXX-SP Series 190 201-XXX-SP-DPDT Series 192 201A Series 200 201A-AU Series 202 202 Series 206 202-200-SP Series 194 232-Insider 104 234-P 108 235P 110 250A Series 208 350 Series 210 355 Series 212 455 Series 214 460 Series 216 460-15-100-LLS 137 460-15-100-SLD 139 460-XXX-SP Series 196 50R Series 188 50R-400-ALT 159 601 Series 218 601-CS-D-P1 220 777 Series 114 777-P2 114 777-AccuPower 123 777-KW / HP-P2 Series 120 777 / 77C Series 118 77C-KW/HP Series 125 A0220 80, 473 AC / DC Earthed System 48 ACBC-120 130 Accessories 467 AC System Monitors / Load Sensors 22, 167 AF0100 79 AF0500 77 Alarm Control / Battery Charger 21, 130 ALT Series 153 ALT-XXX-1-SW / ALT-XXX-3-SW Series 155 Alternating Relays 20, 153 ANSI Device Numbers 506 Appendix – Dimensional Drawings 507 Arc-Flash Protection pg 14, 73 ARP Series 157 ASQU / ASTU Series 270 Brackets & Clips 486 CIO-777-PR 259 CIO-DN-P / CIO-120-DN-P 257 CIO-EN 260 CIO-MB / CIO-120-MB 255 COM 4-20 261 Communication Adapters & Modules 253, 476 CP5 Series 168 CT Application 502 CT Selection Guide 479 CT Series 426 Current Monitoring / Load Sensing Relays 24 Current Monitoring Relays & Transducers 167 Current Transformers 480 Current Transformers Sizing Chart 482 D0920 74 DCSA Series (w / LCSC10T12) 185 Dedicated Timers 28, 262 Dimensional Drawings 507 DIN-Rail & Mounting Adapters 485 DLMU Series 224 DSQU / DSTU Series 272 ECS Series 175 ECSW Series 178 EL3100 44 EL731 48 Electrical Accessories 469 Enclosures & Watertight Covers 487 ERD3425A 391 ERDI Series 362 ERDM Series 275 ESD52233 422 ESDR Series 393 FA / FS Series 455 FB Series 457 FB9L 461 Feeder Protection 14, 69 Find the Right Product for Your Application 2 Flashers 39, 439 Flashers, Beacon Tower 41 Flashers, Photo Control 41 Flashers & Tower Lighting Controls 39, 439 17 Littelfuse.com/relayscontrols 538 © 2022 Littelfuse, Inc. Index ALPHANUMERIC INDEX INDEX FPS pg 71 FPU-32 70 FS100 (low current) Series 442 FS100 (med power) Series 444 FS200 Series 446 FS300 Series 448 FS491 450 FS500 Series 451 FSU1000 Series 440 Generator Ground-Fault Relay 55 GFA300 55 Glossary of Terms 490 Ground Reference Modules 472 Ground-Conductor Monitoring 13, 57 Ground-Fault Circuit Interrupters 53 Ground-Fault Protection 12, 43 High-Tension Couplers 472 HLMU Series 227 HLVA6I23 241 HRDB Series 315 HRDI Series 364 HRDM Series 277 HRDR Series 396 HRDS Series 337 HRPS / HRIS Series 317 HRV Series 437 HSPZA22SL 339 IEEE Device Numbers 506 Industrial Shock-Block 53 Informer 250, 475 Informer-MS 252, 475 Input Modules 473 Instrumentation & Metering Transformers 481 Intrinsically Safe Relays/Pump Controllers 21, 160 Introduction to Protection Relays 493 ISS-100 160 ISS-101 161 ISS-102 Series 163 ISS-105 Series 165 KRD3 Series 398 KRD9 Series 388 KRDB Series 319 KRDI Series 366 KRDM Series 279 KRDR Series 400 KRDS Series 341 KRPD Series pg 424 KRPS Series 281 KSD1 Series 284 KSD2 Series 368 KSD3 Series 402 KSDB Series 321 KSDR Series 404 KSDS Series 343 KSDU Series 286 KSPD Series 406 KSPS Series 288 KSPU Series 370 KVM Series 243 LCSC10T12 185, 473 LCS10T12 / LPM Series 187 Liquid Level Control 19, 129, 478 LLC1 Series 141 LLC2 Series 143 LLC4 Series 145 LLC5 Series 147 LLC6 Series 149 LLC8 Series 151 Load Sensors 22 LSR-0 169 LSR-XXX Series 170 LSRU Series 171 LSRX / LSRX-C Series 173 Motor & Pump Protection 16, 93 Motor & Pump Protection with Bluetooth® 17, 112 Mounting Adapters & Enclosures 483 MP8000 112 MP8100 112 MPS 98 MPS-469X 100 MPU-32 96 MPU-32-X69X 100 MSM Series 291 Multifunction Timers 262 Neutral-Grounding Resistor Chart 61 Neutral-Grounding Resistor Package 66 NGR 66 NGRM-ENC 67, 487 NGR Monitoring 13, 61 ORB Series 323 ORM Series 293 ORS Series 345 17 © 2022 Littelfuse, Inc. 539 Littelfuse.com/relayscontrols Index ALPHANUMERIC INDEX INDEX Overview pg 489 Panel Mount Adapters 483 Personnel Protection 53 PC-102 Series 132 PC-105 133 PC-XXX-LLC-CZ / PC-XXX-LLC-GM 134 PCR Series 465 PGA-1100 81, 469 PGA-LS10 473 PGA-LS20 473 PGA-LS30 473 PGR-3100 45 PGR-3200 46 PGR-4300 45 PGR-6100 94 PGR-6101-120 95 PGR-8800 75 PHS Series 84 PLM Series 231 PLMU11 229 PLR Series 237 PLS Series 239 PRLM Series 295 Product Selection Guide 11 PRS65 347 PTHF4900DK 418 Pump Controls & Liquid Level Controls 18, 129 Relay Application 494 Pump Protection 16, 98 Relay Software 468 Relay Testing Equipment 472 Remote Indication & Meters 473-474 Remote Indication & Monitoring 245, 475 Resistance-Grounded Systems 62, 504 Resistance-Grounding Conversion 503 Resistance Grounding 13, 61 RM1000 Series 246, 475 RM2000 Series 248, 475 RS Series 408 RS485MS-2W 254 SB6000 Series 53 SC3 / SC4 Series 453 SCR Series 459 SCR490D 458 SCR9L 463 SE-105 / SE-107 58 SE-134C / SE-135 pg 59 SE-325 62 SE-330 / SE-330HV 63 SE-330AU 65 SE-601 47 SE-701 50 SE-703 51 SE-704 52 Seal Leak Detectors 18, 129 Sequencing Controls 453 Sensing Resistors 474 Shock-Block GFCI 53 SIO-RTD-02-00 128 SIR Series 86 SLR Series 88 Sockets 488 Software 468 Solidly-Grounded Systems 43, 504 Switching Relays & Controls 15, 83 T10 Series 274 T2D120A15M 428 TA Series 430 TAC1 Series 432 TCR9C 90 TCS Series 181 TCSA Series 183 TDB / T DBH / TDBL Series 325 TDI / TDIH / TDIL Series 372 TDM / TDMH / TDML Series 297 TDMB Series 420 TDR Series 410 TDS / TDSH / TDSL Series 348 TDU / TDUH / TDUL Series 299 TDUB Series 327 TDUI / TDUIH / TDUIL Series 374 TDUS Series 350 Termination & Adapters 477 TH1 Series 301 THC / THS Series 352 THD1B410.5S 303 THD2 Series 376 THD3C42A0 412 THD7 Series 378 THDB Series 329 THDS Series 354 Time Delay Relays 26, 262 17 Littelfuse.com/relayscontrols 540 © 2022 Littelfuse, Inc. Index ALPHANUMERIC INDEX INDEX Timer Function Guide pg 264 Timers, Factory-Programmable 26 Timers, Multifunction 27 Timing Function Symbols 264 TL Series 434 TMV8000 / TSU2000 Series 305 Tower & Obstruction Lighting Controls 39, 41, 439 Trailing Cable Protection 57 TRB Series 331 TRDU Series 265 TRM Series 307 TRS Series 356 TRU Series 268 TS1 Series 309 TS2 / TS6 Series 380 TS441165 313 TSA141300 436 TSB Series 333 TSD1 Series 311 TSD2 Series 382 TSD3411S 414 TSD6 Series 384 TSD7 Series 386 TSD94110SB 390 TSDB Series 335 TSDR Series 416 TSDS Series 358 TSS Series 360 TVM Series 235 TVW Series 233 Typical Suffixes 506 Ungrounded AC Systems 43 Ungrounded DC System 47 Ungrounded System 504 Voltage Monitoring Relays 22, 167 WVM Series 222 Introduction to Protection Relays and Applications Lowering the Limits for Ground-Fault Protection The Importance of Effective Motor and Motor Circuit Protection Ground-Fault Protection with VFDs Selecting an Arc-Flash Relay Why NGRs Need Monitoring Transformer Protection Littelfuse Literature is in the App Store! Our free Littelfuse Catalogs and Literature App keeps our products and technical resources at your finger tips, wherever you are. Find products and technical specifications you need, quickly and easily! White Papers & Technical Information An expanded Technical Application Guide, White Papers, and a library of technical information is available online at Littelfuse.com/TechnicalCenter. Littelfuse can help you address application and circuit protection challenges while achieving regulatory compliance. 17 Kaunas Amsterdam Bellingham Boston Fort Collins Essen Saskatoon Seoul Tokyo Tsukuba Suzhou Wuxi Beijing Noida Seongnam Shanghai Kunshan Taipei Chu-pei Dongguan Shenzhen Hong Kong Lipa City Singapore São Paulo Taguig Legnago Bremen Lampertheim Deventer Charneca de Caparica Chippenham San Sabastian LeidenLauf Ozegna Burlington Beverly Troy Muzquiz Matamoros Piedras Negras Eagle Pass Manaus Rapid City Lake Mills Rock Falls Chicago Mount Prospect Champaign Fremont Aliso Viejo Long Beach Milpitas Orange Santa Clara LOLocal Resources for a CAL RESOURCES FOR A GLOBGLOBAL AL MARKET Market Visit Technical Resources at Littelfuse.com Technical information is only a click away. The Littelfuse Technical Resources contains datasheets, product manuals, whitepapers, application guides, demos, on-line design tools, and more. Fuses and Fuse Holders Catalog (PF101N) Littelfuse offers a complete circuit protection portfolio of industrial power fuses, including time-saving indication products for an instant visual blown-fuse identification. An Extension of Your Team Technical Hotline (800-TEC-FUSE or 800-832-3873) Littelfuse engineers are a phone call away to help identify potential issues and provide product recommendations to resolve problems. Application and Field Support Our experienced product and application engineers work step-by-step with customers from design to installation to determine the best solution. POWR-GARD® Solar Catalog (PF140N) POWR-GARD Solar Products are designed specifically for photovoltaic applications where issues such as heat, efficiency, longevity and global standards impact the choices in selecting circuit protection. © 2022 Littelfuse, Inc. FORM PF130N Rev: 3-A-041922 Littelfuse products are certified to many standards around the world. 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