Sel321 Pott Dcb

Application Guide Volume I AG2017-22Using an SEL-321 and an SEL-311 Series Relay to Set Up POTT and DCB Schemes Jared Candelaria and Hardesh Khatri INTRODUCTION In 1993, SEL introduced the SEL-321 Phase and Ground Distance Relay, and it has been widely used to provide pilot protection on transmission lines ever since. Now, over 20 years later, many of these relays are still in service and in good working order. However, as utilities upgrade their systems, the SEL-321 is being replaced by relays that include additional functionality. It is not uncommon for these upgraded relays to be installed on a tie in which each end of the line is owned by a different utility. Occasionally, one utility upgrades its terminal as part of a new standard relaying package, while the other chooses to keep its existing protection. Even though the terminals have dissimilar relays, losing pilot protection is not acceptable. This application guide details how to program the SEL-321 and SEL-311 Series Relays in order to maintain pilot protection by using either a Permissive Overreaching Transfer Trip (POTT) or Directional Comparison Blocking (DCB) scheme. This application guide can be applied to the SEL-311C Transmission Protection System, the SEL-311L Line Current Differential Protection and Automation System, and the SEL-311M Line Current Differential Protection and Automation System. For the examples in this guide, we use the SEL-311C to represent all SEL-311 Series Relays. We assume the reader has a basic understanding of pilot protection, so this application guide does not go into detail on the schemes. For an in-depth discussion of POTT and DCB schemes, refer to [1] and [2]. NOTE: POTT and DCB schemes are not available on the SEL-311A Phase and Ground Distance Relay, the SEL-311B Distance Relay With Recloser, or the SEL-311C Advanced Distance Relay With Recloser. SAMPLE SYSTEM Figure 1 shows a typical two-terminal system. Relay 1 is an SEL-311C that has recently been upgraded, and Relay 2 is an existing SEL-321. The two relays communicate through a fiber-optic connection to implement POTT and DCB schemes. RELAY 1 RELAY 2 PORT 2 (EIA-232) PORT 2 (EIA-232) OPTICAL FIBER TX RX RX TX Figure 1 MIRRORED BITS Communications via a Direct Fiber-Optic Connection Date Code 20170803 SEL Application Guide 2017-22 however. The SEL-311C supports two separate MIRRORED BITS channels (Channels A and B). thus RXDFLT = XXXXXXX1. at a baud rate of 9600. The SEL-321 channel is compatible with either of the SEL-311C channels.. CBADPU PPM MIRRORED BITS Channel Bad 1000 CBAD asserts if the ratio of channel Pickup downtime to total time exceeds this value. RMBxDOd MIRRORED BITS RMBx Dropout 1 Number of received messages before Debounce Messages RMBx drops out. For direct fiber communication. d x = 1 to 8. TX_ID MIRRORED BITS Transmit Identifier 1 Must match the receive identifier of the remote relay. -4 and the SEL-321-5 are limited to 9600. Only in the SEL-321-0. the SEL-2800 Fiber-Optic Transceiver or SEL-2812 Fiber-Optic Transceiver With IRIG-B). thus RXDFLT = XXXXXXX0. Table 1 and Table 2 provide example setting values for Port 2 on the SEL-321 and SEL-311C. in a DCB scheme you can set the default state of the block bit (RMB1) to 1. which uses an 8-data bit format. while the SEL-321 supports one channel. c To maintain security during loss of communications. RTS_CTS Enable Hardware Handshaking N Not needed for relay-to-relay communication. SPEED Communications Baud Rate 9600b The SEL-321-3. 2 PORT SETUP To ensure that the relays can properly communicate with each other. a MB uses a 7-data bit format for data encoding. if PROTOCOL = MBG. RMBxPUd MIRRORED BITS RMBx Pickup 1 Number of received messages before Debounce Messages RMBx picks up. sends and receives MIRRORED BITS two times per power system cycle.g. set up a serial port on each relay for MIRRORED BITS® communications. See [3] for further information. RBADPU MIRRORED BITS Receive Bad 60 A channel error must last 60 s before Pickup RABD is asserted. in a POTT scheme you can set the default state of the permissive receive bit (RMB1) to 0. MB works adequately. b The SEL-321. RX_ID MIRRORED BITS Receive Identifier 2 Must match the transmit identifier of the remote relay. The port setup is identical for both POTT and DCB schemes. use fiber-optic transceivers to convert serial to fiber (e. select the MB8 protocol setting if additional communications interface equipment is used on the channel. -1. The other option is MB8. RXDFLT MIRRORED BITS Receive Default XXXXXXXXc The default state in place of received data Status in error condition. SEL Application Guide 2017-22 Date Code 20170803 . Table 1 SEL-321 Port 2 Settings Setting Name Value Comment PROTOCOL Communications Protocol MBa Enables MIRRORED BITS communications. For direct fiber applications. then you can set RMBx from Group settings instead of Global settings. respectively. e MIRRORED BITS RMB Pickup 1 Number of received messages before RMBx Debounce Messages picks up. When you have set up the ports on both relays and connected the communications cable. 3 Table 2 SEL-311C Port 2 Settings Setting Name Value Comment EPORT Enable Port Y The port must be enabled to set up communication. b Ensure the baud rate of the SEL-311C matches the baud rate of the SEL-321. c To maintain security during loss of communications.b RTSCTS Enable Hardware N Not needed for relay-to-relay communication. the RXID and TXID settings will move from the Port settings to the Group settings. MB8B. MB8B. when asserted. MBGA. thus RXDFLT = XXXXXXX1. or MBGB protocol if additional communications interface equipment is used on the channel. however. in a POTT scheme you can set the default state of the permissive receive bit (RMB1A) to 0. sends and receives MIRRORED BITS four times per power system cycle. indicate that the MIRRORED BITS communications channel is operational and ready to transmit and receive data. in a DCB scheme you can set the default state of the block bit (RMB1A) to 1. verify the status of the channel. thus RXDFLT = XXXXXXX0. RMBxDOd. PROTO Communications Protocol MBAa Enable MIRRORED BITS communications on Channel A. respectively. These bits. RMBxPUd.e MIRRORED BITS RMB 1 Number of received messages before RMBx Dropout Debounce Messages drops out. MBA and MBB work adequately. and MBGB. The other options are MB8A. RBADPU MIRRORED BITS Rx Bad 60 (Default) A channel error must last 60 s before RABD is Pickup Time asserted. a MBA and MBB use a 7-data bit format for data encoding. RXDFLT MIRRORED BITS Receive XXXXXXXXc The default state in place of received data in Default Status error condition. d The SEL-311C. e x = 1 to 8. CBADPU PPM MIRRORED BITS 1000 (Default) CBAD asserts if the ratio of channel downtime Channel Bad Pickup to total time exceeds this value. Do this by targeting the ROK Relay Word bit in the SEL-321 (TAR 20 com- mand) and the ROKA Relay Word bit in the SEL-311C (TAR ROKA command). Handshaking TXID MIRRORED BITS transmit 2 Must match the receive identifier of the remote identifier relay. For direct fiber applications. at a baud rate of 9600. Figure 2 and Figure 3 display the expected responses to the commands. which use an 8-data bit format. RXID MIRRORED BITS receive 1 Must match the transmit identifier of the remote identifier relay. select the MB8A. See [3] for further information. If PROTO = MBGA or MBGB. SPEED Communications Baud Rate 9600 The SEL-311C-0 and SEL-311C-1 are limited to 38400 and 57600. MBGA. =>>TAR 20 RBAD CBAD LBOK ROK * * * TOP 0 0 0 1 0 0 0 0 Figure 2 Status of the ROK Bit in the SEL-321 =>>TAR ROKA LBOKB CBADB RBADB ROKB LBOKA CBADA RBADA ROKA 0 0 0 0 0 0 0 1 Figure 3 Status of the ROKA Bit in the SEL-311C Date Code 20170803 SEL Application Guide 2017-22 . This causes the output AND 1 (shown in Figure 5) to assert. or both. For more in-depth information. while the reverse-looking Zone 3 element remains deasserted. the Zone 2 at Relay 1 asserts and Zone 3 deasserts. directional overcurrent elements. which causes a Key to transmit and the top input to AND 2 to assert. Again. the top input into AND 3 remains deasserted and does not allow a high-speed trip. This causes the output of AND 4 to assert. both outputs (AND 2 and AND 3) assert. AND 1 asserts. At Relay 2. which does not allow a high-speed trip. AND 4 is not true and a Key is not sent to Relay 1. it can only provide accelerated tripping if it receives permission from the remote end. Zone 2 at Relay 2 also asserts. and a reverse-looking zone (Zone 3) blocks sending the permission. As another example. 4 RELAY ELEMENTS Pilot schemes use forward-looking overreaching elements and reverse-looking elements. At the same time. In this scenario. the overreaching Zone 2 element at Relay 1 asserts. Zone 2 sends the permissive signal to the remote terminal. At Relay 2. At this point. consider a fault at F2 (shown in Figure 4). as Figure 4 shows. while the Zone 3 element remains deasserted. sending a permissive trip signal (Key) to Relay 2 and causing the top input into AND 2 to be true. Relay 1 must receive a Key from Relay 2 to trip. When a forward-looking overreaching zone (Zone 2) asserts. Table 3 Common Pilot Scheme Relay Elements Relay Element Description M2P Zone 2 phase mho forward distance element Z2G Zone 2 ground mho distance element 67G2 Level 2 residual ground overcurrent forward element 67Q2 Level 2 negative-sequence forward overcurrent element M3P Zone 3 mho phase reverse distance element Z3G Zone 3 ground mho distance element 67G3 Level 3 residual ground reverse overcurrent element 67Q3 Level 3 negative-sequence reverse overcurrent element POTT OVERVIEW A POTT scheme is a communications scheme in which an asserted overreaching element at the local terminal must receive permission to trip from the remote terminal. while the Zone 3 element asserts. the Zone 2 element remains deasserted. For example. sending a Key to Relay 1 and causing the top input to AND 3 to be true. even though the bottom input of AND 3 has received a Key. Table 3 lists the most commonly used relay elements for pilot schemes. NOTE: The preceding section provides an overview of POTT schemes. which causes the relays to trip with no intentional delay. When each relay receives a Key from the remote end. As a result. if a fault occurs at point F1. you can use distance elements. To set this up. refer to [1]. SEL Application Guide 2017-22 Date Code 20170803 . respectively. Table 4 SEL-321 POTT Settings Setting Name Value Description EPOTT Enable Permissive Y Enables the POTT logic. you must enable the logic in both relays. 5 F1 F2 RELAY 1 RELAY 2 OPTICAL FIBER TX RX RX TX ZONE 3 ZONE 2 ZONE 2 ZONE 3 Figure 4 MIRRORED BITS Communications via a Direct Fiber-Optic Connection KEY KEY XMTR XMTR ZONE 2 ZONE 2 AND 1 AND 4 ZONE 3 AND 2 TRIP TRIP AND 3 ZONE 3 KEY KEY RCVR RCVR RELAY 1 RELAY 2 Figure 5 Simplified POTT Logic POTT SETUP In order to set up a POTT scheme in the SEL-321 and SEL-311C. The settings in both the relays are mostly similar. Table 4 and Table 5 provide a summary of how to set up the POTT logic in the SEL-321 and SEL-311C. EWFC Weak-Infeed Enable N (Default) Allows echo keying in the event of a weak terminal or an open breaker (requires EVOLT = Y). with some differences. Date Code 20170803 SEL Application Guide 2017-22 . ETDPU Echo Time Delay Pickup 2 (Default) Sets the minimum time requirement for received permissive trip before echo begins. EDURD Echo Duration Time Delay 4 (Default) Limits echo duration to prevent channel lockup. EBLKD Echo Block Time Delay 10 (Default) Prevents echoing of a received permissive trip for a settable delay after dropout of local permissive elements. Overreaching Transfer Trip Z3RBD Zone 3 Reverse Block Delay 5 (Default) Prevents a POTT scheme misoperation during current reversal. in the SEL-311C. SEL recommends setting both of these equations by using the same elements so that each terminal responds similarly to fault conditions. In the SEL-321. wire a 52A to IN101. To program the logic. in the SEL-311C. Do this by mapping the permissive trip to the received Mirrored Bit. ➤ The relays must be programmed to map the KEY from the remote end into the POTT logic. 6 Table 5 SEL-311C POTT Settings Setting Name Value Description ECOMM Communications-Assisted POTT Enables the POTT logic. IN1 Input Contact 1 Assignment 52A1 Assign to the circuit breaker 52A status. EBLKD Echo Block Time Delay 10 (Default) Prevents echoing of a received permissive trip for a settable delay after dropout of local permissive elements. Trip Scheme Z3RBD Zone 3 Reverse Block 5 (Default) Prevents a POTT scheme misoperation during current Delay reversal. EDURD Echo Duration Time Delay 4 (Default) Limits echo duration to prevent channel lockup. ETDPU Echo Time Delay Pickup 2 (Default) Sets the minimum time requirement for received permissive trip before echo begins. Table 6 SEL-321 POTT Logic Settings Setting Name Value Comment MTCS Mask for Trip Communications M2P + Z2G The elements that allow high-speed. in the SEL-311C. a Because PROTOCOL = MB. Set each of these elements to KEY. the equation for the communications-assisted trip conditions is MTCS. set OUT1 to 3PT. you must program the elements that qualify a communications-assisted trip. In the SEL-321. set OUT101 to TRIP. POTT LOGIC When you have enabled each relay for a POTT scheme. Scheme Variable (Default) communications-assisted tripping. consider the following: ➤ In the SEL-321. ➤ You should wire a breaker contact status to each relay. in the SEL-311C the equation is TRCOMM. TMB1 Transmit Mirrored Bit 1 KEY Send a permissive trip to the remote end. ➤ A tripping output must be assigned to trip each relay's respective circuit breaker. send it via TMB1A. program RMB1 to PT. In the SEL-321. send the permissive trip signal via TMB1. ➤ Each relay must be able to transmit a permissive trip signal. EWFC Weak-Infeed Enable N (Default) Allows echo keying in the event of a weak terminal or an open breaker. SEL Application Guide 2017-22 Date Code 20170803 . a RMB1 Receive Mirrored Bit 1 PT Receive a permissive trip from the remote end. OUT1 Output Contact Logic OUT1 3PT Trip output to the circuit breaker. program PT1 to RMB1A. in the SEL-321. This improves the three-pole open logic. In the SEL-321. wire a 52A contact to IN1. set RMB1 in the Global settings. 7 Table 7 SEL-311C POTT Logic Settings Setting Name Value Comment TRCOMM Communications-Assisted Trip M2P + Z2G The elements that allow high-speed. A reverse-looking zone (Zone 3) at the remote terminal sends the blocking signal. it trips at high speed. When a forward- overreaching zone (Zone 2) at the local terminal asserts. unless it receives a blocking signal from the remote end. TMB1A Transmit Channel A Mirrored Bit 1 KEY Send a permissive trip to the remote end. PT1 Permissive Trip 1 Equation RMB1A Receive a permissive trip from the remote end. 52A Circuit Breaker Status Equation IN101 Assign to the circuit breaker 52A status. KEY KEY (TMB1A) (TMB1) TRCOMM MTCS TRIP 3PT PT1 PT (RMB1A) (RMB1) ZONE 3 ZONE 3 3PO SEL-311C SEL-321 3PO Figure 6 Simplified POTT Logic Between the SEL-321 and SEL-311C (+) (+) (+) (+) SEL-311C A01 A17 SEL-321 218 201 (Partial) (Partial) OUT101 IN101 OUT1 IN1 A02 A18 217 202 Circuit 52A 52A Circuit 52A 52A Breaker Breaker (Partial) (Partial) 52TC 52TC (–) (–) Figure 7 Simplified Relay Wiring DCB OVERVIEW A DCB scheme is a communications scheme in which an asserted overreaching element at the local terminal must receive a blocking signal from the remote terminal to not trip. Date Code 20170803 SEL Application Guide 2017-22 . Conditions (Default) communications-assisted tripping. OUT101 Output Contact 101 Equation TRIP Trip output to the circuit breaker. Again. For more in-depth information. refer to [2]. Because Zone 3 is deasserted. In this scenario. The assertion of Zone 2 starts TIMER 1 (see Figure 8). At Relay 2. this application guide does not discuss or include nondirectional starting. both relays identify the fault in their respective Zone 2 and do not receive a block signal from the remote end. consider a fault at point F2 (see Figure 4). Zone 2 remaining deasserted causes AND 2 to not allow a high-speed trip. If the top input in AND 1 is true and Relay 1 has not received a block from the remote end. the top input into AND 2 becomes true. Relay 2 does not send a block signal to Relay 1. Relay 1 does not send a block signal to Relay 2. and Zone 3 remains deasserted. Because Zone 3 remains deasserted. even though Relay 1 does not send a block signal. 8 As Figure 4 shows. and Zone 2 starts TIMER 2. Relay 1 does not send a block signal to Relay 2. The settings in both the relays are mostly similar. then the top input into AND 1 becomes true. respectively. At Relay 2. you must enable the logic in both relays. As another example. with some differences. Zone 3 asserts. ZONE 3 ZONE 3 BLOCK XMTR BLOCK XMTR TIMER 1 TIMER 2 CTD CTD ZONE 2 ZONE 2 AND 1 TRIP TRIP AND 2 BLOCK BLOCK RCVR RCVR RELAY 1 RELAY 2 Figure 8 Simplified DCB Logic DCB SETUP To set up a DCB scheme in the SEL-321 and SEL-311C. At Relay 2. and Zone 2 starts TIMER 1. Note that these settings only apply to directional starting. If Zone 2 is asserted for longer than the programed timer delay (CTD) in TIMER 1. In this scenario. the overreaching Zone 2 element at Relay 1 asserts. This causes the AND 1 to not allow a high-speed trip. If the top input in AND 2 is true and Relay 2 has not received a block from the remote end. and assertion of Zone 3 sends a block to Relay 1. NOTE: The preceding section provides an overview of DCB schemes. if a fault occurs at point F1. If Zone 2 is asserted for longer than the programed timer delay (CTD) in TIMER 2. Zone 2 at Relay 1 asserts. which allows both relays to trip their respective breakers and clear the line at high speed. Table 8 and Table 9 provide a summary of how to set up the DCB logic in the SEL-321 and SEL-311C. and Zone 3 remains deasserted. then Relay 1 will issue a trip. SEL Application Guide 2017-22 Date Code 20170803 . then Relay 2 issues a trip. Zone 2 deasserts. Zone 2 asserts and Zone 3 remains deasserted. Delay note 67N2SD 67N Coordination Time Delay See following Delays 67N2 element output. BTXD Block Trip Receive Extension Delay 1 Sets the reset time of a block trip received condition after the reset of block trip input. the SEL-321 should send an instantaneous block when Zone 3 picks up or when the START bit asserts. However. note 67Q2SD 67Q Coordination Time Delay See following Delays 67Q2 element output. BTXD Block Trip Receive Extension Delay 1 (Default) Sets the reset time of a block trip received condition after the reset of block trip input. You must delay the CTD at the faster relay to coordinate with the slower relay's blocking elements. The CTD must be greater than the communications channel delay. Blocking Z3XD Zone 3 Pickup Extension Time Delay 5 (Default) Prevents a DCB scheme misoperation during current reversal. Coordination Time Delay note 67SD 67G and 67Q Coordination Time See following Delays 67G2 and 67Q2 element outputs. note Table 9 SEL-311C DCB Settings Setting Name Value Description ECOMM Communications-Assisted Trip DCB Enables the DCB logic. Delay note Z2GSD Zone 2 Ground Coordination Time See following Delays Z2G element output. 9 Table 8 SEL-321 DCB Settings Setting Name Value Description EDCB Enable Directional Comparison Y Enables the DCB logic. there is no time delay in the SEL-311C. so SEL recommends setting these to a similar value in both the relays. Z2PSD Zone 2 Phase Coordination Time See following Delays M2P element output. Delay note NOTE: When determining the coordination time delay (CTD). There is an inherent two-cycle delay in the SEL-321 from the time Zone 3 picks up and the blocking (START) bit asserts. it sends the block instantaneously when Zone 3 picks up. All other time delays are dropout times. the Zone 2 coordination time delays can be set the same on both the relays. For both the SEL-321 and SEL-311C you can find this information in their respective instruction manuals. Z3XPU is present only in the SEL-311C and behaves as a guard against current reversal. you must evaluate the operating time of the tripping elements. Scheme Z3XPU Zone 3 Reverse Pickup Time Delay 1 (Default) Current reversal guard pickup timer. Date Code 20170803 SEL Application Guide 2017-22 . In this situation. plus some additional margin. To ensure proper coordination between these relays. You should add all of this to the communications channel delay. 21SD Zone 2 Phase and Ground See following Delays M2P and Z2G element outputs. Z3XD Zone 3 Pickup Extension Time Delay 5 (Default) Prevents a DCB scheme misoperation during current reversal. You must consider both the SIR and distance from the relay. in the SEL-311C. and SEL-321-3. set RMB1 in the Global settings. in the SEL-311C. This improves the three-pole open logic. OUT1 Output Contact Logic OUT1 3PT Trip output to the circuit breaker. To program the logic. When used with any other SEL-321. Table 11 SEL-311C DCB Logic Settings Setting Name Value Comment a TRCOMM Communications-Assisted Trip Z2PGS Elements that allow high-speed. you must program the elements that qualify a communications-assisted trip. In the SEL-321. 52A Circuit Breaker Status Equation IN101 Assign to the circuit breaker 52A status. b ORDER = QV when used with the SEL-321-5. ➤ Each relay must be able to transmit a block signal. set the SEL-311C to use only the negative-sequence voltage polarization (ORDER = Q). wire a 52A to IN101. -1. In the SEL-321. or zero-sequence current polarization. To prevent miscoordination. SEL recommends setting both equations by using the same elements so each terminal responds similarly to fault conditions. set the SEL-311C to use negative. ORDER = Q when used with any other SEL-321. the SEL-321-5 has both negative. TMB1A Transmit Channel A Mirrored Bit 1 DSTRT Send a block signal to the remote end. in the SEL-311C. it is TRCOMM.The SEL-321-0. a Because PROTOCOL = MB. consider the following: ➤ In the SEL-321. SEL-321-2. M2P + Z2G (Default) Elements that allow high-speed. ➤ The relays must be programmed to map the BLOCK from the remote end into the DCB logic. 10 DCB LOGIC When you have enabled each relay for a DCB scheme. Conditions communications-assisted tripping. OUT101 Output Contact 101 Equation TRIP Trip output to the circuit breaker. TMB1 Transmit Mirrored Bit 1 START + M3P + Z3G Send a block signal to the remote end. In the SEL-321. send it via TMB1A. SEL Application Guide 2017-22 Date Code 20170803 . In the SEL-321. program RMB1 to BT. in the SEL-311C. a In the DCB logic. Table 10 SEL-321 DCB Logic Settings Setting Name Value Comment MTCS Mask for Communications.and zero-sequence voltage polarization when used with an SEL-321-5 (ORDER = QV). set OUT1 to 3PT. -4 only have negative-sequence voltage polarization. Do this by mapping the BLOCK to the received Mirrored Bit. the equation for the communications-assisted trip conditions is MTCS. BT Block Trip Equation RMB1A Receive a block signal from the remote end. zero- sequence voltage. wire a 52A contact to IN1. ➤ Note the polarization choices for the directional element in the SEL-321. RMB1a Receive Mirrored Bit 1 BT Receive a block signal from the remote end. ➤ You should wire a breaker contact status to each relay. b ORDER Ground Directional Priority See note Set to match the SEL-321. use Z2PGS instead of M2P + Z2G to provide the individual carrier coordination timers for the Level 2 directional elements. send the block signal via TMB1.and zero-sequence voltage polarization. in the SEL-311C. the SEL-311C allows you to choose a combination of negative-sequence voltage. set OUT101 to TRIP. IN1 Input Contact 1 Assignment 52A1 Assign to the circuit breaker 52A status. Assisted Tripping communications-assisted tripping. ➤ A tripping output must be assigned to trip each relay’s respective circuit breaker. program BT to RMB1A. ➤ Verify that the directional elements and pickup settings at each line terminal have sufficient operating quantities to detect both internal and external faults. be aware of the capabilities of both relays. SEL does not recommend connecting dissimilar relays for pilot protection. the SEL-321 and SEL-311 Series Relays. match the directional and protective element sensitivities at both line ends. Some important factors to consider are the following: ➤ If possible. but if there is a need to do so. Date Code 20170803 SEL Application Guide 2017-22 . in this case. Use the same protective elements at each line end whenever possible. 11 TRCOMM MTCS TRIP 3PT BT (RMB1A) BT (RMB1) ZONE 3 ZONE 3 DSTRT (TMB1A) START (TMB1) SEL-311C SEL-321 Figure 9 Simplified DCB Logic Between the SEL-321 and SEL-311C (+) (+) (+) (+) SEL-311C A01 A17 SEL-321 218 201 (Partial) (Partial) OUT101 IN101 OUT1 IN1 A02 A18 217 202 Circuit 52A 52A Circuit 52A 52A Breaker Breaker (Partial) (Partial) 52TC 52TC (–) (–) Figure 10 Simplified Relay Wiring CONCLUSION This application guide discusses the settings and configuration requirements to connect two dissimilar relays. for implementing POTT and DCB schemes. and set reverse- reaching elements at a greater sensitivity than remote overreaching elements. ” SEL Application Guide (AG95-29). Guzman. “Applying the SEL-321 Relay to Permissive Overreaching Transfer Trip (POTT) Schemes.com © 2017 by Schweitzer Engineering Laboratories. All brand or product names appearing in this document are the trademark or registered 2350 NE Hopkins Court • Pullman. trademark of their respective holders. Inc.S.com.332. 2014. SEL Application Guide 2017-22 Date Code 20170803 . Roberts.com info@selinc. Tel: +1. 1993.332.S. 2350 NE Hopkins Court Pullman. selinc.S. Behrendt and K. McDaniel. “Applying the SEL-421 Relay to Permissive Overreaching Transfer Trip Schemes.A. 2007.7990 permission. If you have questions or comments.com.3838 Fax: +1. [3] K. Available: selinc. Available: selinc. 2010. Available: selinc. please contact us at: Schweitzer Engineering Laboratories.com • info@selinc. All rights reserved. Inc.509. J.338. Roberts.1890 • Fax: +1.A.7990 selinc.” SEL Application Guide (AG93-06). “Applying the SEL-321 Relay to Directional Comparison Blocking (DCB) Schemes.com. [4] R.” SEL Application Guide (AG2010-01). No SEL trademarks may be used without written Tel: +1. WA 99163-5603 U.509. WA 99163-5603 U. and Foreign patents.509. FACTORY ASSISTANCE We appreciate your interest in SEL products and services. Fodero. Available: selinc.com SEL products appearing in this document may be covered by U. and K.com. Zimmerman. “Implementing MIRRORED BITS Technology Over Various Communications Media” SEL Application Guide (AG2001-12).509. 12 REFERENCES [1] A. [2] J.332.