Setting SEL-321 Relays

in the

Computer-Aided Protection Engineering System (CAPE)

Prepared for

CAPE Users Group

Revised October 1, 2001 Revised November 11, 2008

Electrocon International, Inc. Ann Arbor, Michigan

This document is the sole property of Electrocon International, Inc. and is provided to the CAPE Users Group for its own use only. It may not be supplied to any third party, or copied or reproduced in any form, without the express written permission of Electrocon International, Inc. All copies and reproductions shall be the property of Electrocon International, Inc. and must bear this ownership statement in its entirety.

Application Note on Setting SEL-321 Relay

I. Relay Models A. Description The CAPE library model in cape_starter.gdb includes the following features: Four zones of phase and ground mho elements plus four zones of ground distance

quadrilateral elements, each reversible, with independent phase and ground timers Positive-sequence memory voltage polarization Four residual and negative-sequence overcurrent elements with negative-sequence

directional control Phase, sequence, and ground time-overcurrent elements for backup protection Negative-sequence directional element Adaptive ground directional element choosing between negative- and zero-sequence

quantities (SEL-321-5) Load-encroachment logic to suppress phase elements Voltage elements The following features are not modeled specially in the SEL-321: Single-phase elements Single-pole tripping and phase selection (SEL-321-5) Weak-infeed logic Remote-end-just-opened (REJO) logic, using 50A, 50B, 50C and 3P50 IOC elements Mirrored Bit communications-aided tripping schemes (pilot schemes can be modeled

using the CAPE AUX elements instead) Fault Locating SELOGIC control equations (use CAPE contact logic instead) Power-swing blocking and tripping (but the out-of-step elements can be plotted in CAPE

CG)

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Internal supervision of phase distance zones 1-4 by the Loss-of-Potential Logic, Single-

Pole Open Logic, and Out-of-Step Blocking Logic Zone 1 extension Switch-Onto-Fault Logic Loss-of Potential and Stub Protection Logic B. Updates in the August 2001 Version You can continue to use your existing relay STYLEs, or you can replace the older STYLES with the SEL-321-1 or SEL-321-5, without losing your system settings. The database editor can compare any two STYLEs to show the taps that are different. The new STYLEs are: STYLE Rated current SEL-321-1_5A 5.0 A SEL-321-1_1A 1.0 A SEL-321-5_5A 5.0 A SEL-321-5_1A 1.0 A The newer CAPE model includes: TIMERs set from the common taps. 59PBD and 59PRD overvoltage timers Separate left and right LOAD elements ZLIN and ZLOUT Adaptive directional element for ground faults (SEL-321-5 only) VOLT and AUX elements Various informational taps from the current Schweitzer SEL-5010 database The following older STYLES are no longer distributed to new users in the database cape_starter.gdb. SEL-321-R100 5.0 A Base relay ; no timer taps SEL-321-R101 5.0 A Base relay with additional informational taps; no timer

taps SEL-321-R101_1A 1.0 A 1-Amp version of SEL-321-R101; no timer taps SEL-321-1-R101 5.0 A Older version of SEL-321-1_5A. II. Relay Elements The logic for zone 1, 2 or 3 is as follows:

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TRIPPING LOGICORPILOT SIGNAL

PHASEDISTANCE

GROUNDDISTANCE

INSTANTANEOUSOVERCURRENT

GROUND TIMEOVERCURRENT

50L

50G

32Q

50N

32Q

50Q

32Q

32Q

21G

50PP

21P32QF

50ABC

67N

51NP

67Q

51N

INSTANTANEOUSOVERCURRENT

III. Element Settings All element settings, except for contact logic, are taken from the common taps. If you change a setting or drag a curve, CAPE automatically changes the corresponding common taps. A. CT and VT Connections When you place a relay style in your system, you will have to choose an appropriate operating CT and VT. This can be done by clicking on the Connect Op CT button in the relay setting form of the Database Editor, and choosing a suitable CT from the list shown. If no CT exists, you will have to create one. The CT you choose will be assigned to all elements that need a current input. For the voltage input, click on the Connect Op VT button and choose an appropriate VT. The SEL-321 does not require a separate directional polarizing VT or polarizing CT, because CAPE stores the negative-sequence directional elements as distance elements (with ZONE_CHARAC_UNIT_1 defined as DIRECTIONAL). Do not change the CT and VT quantities; CAPE copies the defaults from the database library.

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B. Negative-Sequence Directional Elements 32QF and 32QR The relay measures the apparent impedance

Z Re VI

e2 22

jMTA= FHGIKJ

The MTA is the tap setting Z1ANG. For forward faults, Z2 is usually negative and must be less than the tap setting Z2F. For reverse faults, Z2 is positive and must be greater than Z2R. For the optimum MTA, the positive-sequence line angle is a good approximation. CAPE models these elements as DIST elements. All settings are made from the relay common taps. You do not have to visit the individual element setting forms. You must set the common taps as follows: Z2F (Largest -seq source impedance component for forward faults) 50QF (3I2 pickup for forward faults) Z2R (Least -seq source impedance component for reverse faults) 50QR (3I2 pickup for reverse faults) a2 least unbalance I2/I1 for operation See [1] for setting rules, or use the CAPE Relay Setting macro sel_321_nseq. C. Distance Elements Reach and torque angle settings are made from the relay common taps. You do not have to visit the individual element setting forms. CAPE does not allow external supervision in the SEL-321. The DIST elements are already internally supervised and the present code allows only one supervisor per element. To set the DIST elements you specify the common taps, which are listed in detail below. The important settings are: Enabling taps PMHOZ, GMHOZ and QUADZ (N,1,2,3,4). The default for these is N

(no operation). A single line angle (MTA) set as Z1ANG degrees for all zones. Zone reach (secondary ohms). For zone 1, for example, Z1P, Z1MG and XG1 are all

measured from the R-X origin to the MHO circle or QUAD reactance line in the MTA direction.

Zero-sequence compensation taps (complex k0) for the GROUND DIST elements: k01M,

k01A for zone 1 and k0M, k0A for zones 2, 3 and 4.

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Nonhomogeneous system compensation angle T for the ground quadrilateral element. Pickup taps for internal overcurrent supervision: 50PP phase and 50L and 50G ground. Negative-sequence directional elements, which supervise the distance elements except

when three-phase faults are detected. Timer settings for phase and ground elements. The elements are: DIST M1P Zone 1 Phase Mho characteristic DIST M2P Zone 2 DIST M3P Zone 3 DIST M4P Zone 4 DIST Z1G Zone 1 Ground distance with Mho and Quad units DIST Z2G Zone 2 DIST Z3G Zone 3 DIST Z4G Zone 4 DIST OOS Zone 5 Out-of-step blocking element, modeled for CG only DIST OOS Zone 6 DIST ZLIN Zone 1 Left part of ZLOAD characteristic; operates only for positive-

sequence current > 0.1 * rated current and for arg(Z1) between 90 and 270 degrees (inward load)

DIST ZLOUT Zone 1 Right part of ZLOAD characteristic; operates only for positive-

sequence current > 0.1 * rated current and for arg(Z1) between -90 and 90 degrees (outward load)

Phase distance zones 1-4 are also supervised internally by the directional element 32QF or 32QR; these constraints are in the program code. Operation of phase distance zones 1-4 is blocked by operation of either ZLOAD element when Load-Encroachment Logic is enabled (tap ELE = Y). This constraint is in the program code. Ground distance zones 1-4 are also supervised internally by the directional element 32QF or 32QR; these constraints are in the program code. For DIST elements, you may set the Desired Primary Ohms and angle (degrees) for informational purposes only.

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D. Instantaneous Overcurrent To set the IOC elements you specify the pickups, torque control and timer settings as common taps. Also set the Enabling taps E50N and E50Q (N,1,2,3,4). The following supervise the distance zones: IOC 50PP1 for mho phase distance supervision IOC 50PP2 IOC 50PP3 IOC 50PP4 IOC 50L1 for phase current IOC 50L2 IOC 50L3 IOC 50L4 IOC 50G1 for residual current IOC 50G2 IOC 50G3 IOC 50G4 There are four levels of instantaneous overcurrent protection. The CAPE model treats directional and non-directional IOC elements separately; use either in the contact logic. IOC 50N1 Non-directional; instantaneous only IOC 50N2 IOC 50N3 IOC 50N4 IOC 50Q1 IOC 50Q2 IOC 50Q3 IOC 50Q4 IOC 67N1 50N with internal supervisor DIR 32QF or 32QR;

instantaneous or time-delayed IOC 67N2 IOC 67N3 IOC 67N4 IOC 67Q1 50Q with internal supervisor DIR 32QF or 32QR;

instantaneous or time-delayed IOC 67Q2 IOC 67Q3 IOC 67Q4

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Additional elements: IOC 50H High-set phase overcurrent IOC 50M Medium-set phase overcurrent IOC 50ABC (+seq for out-of-step blocking) F. Phase and Ground Time Overcurrent 1. Elements To set the TOC elements you specify the curve type, pickup, time dial setting and torque-control choice as common taps. Also set the Enable taps E51N and E51Q. You do not have to visit the individual element setting forms. The elements are: TOC 51P internal supervisor tap-selectable (M2P, ZLIN, ZLOUT,

None) TOC 51N internal supervisor tap-selectable (32QF, 32QR, Z2G, None) TOC 51Q internal supervisor tap-selectable (32QF, 32QR, M2P, Z2G,

None) The alternative time-overcurrent curves are [1]: CHARACTERISTIC CAPE database name Common Tap Setting U1: Moderately Inverse US_MOD_INVERSE_501 U1 U2: Inverse U.S. Inverse U2 U3: Very Inverse U.S. Very Inverse U3 U4: Extremely Inverse U.S. Extrem. Inverse U4 C1: Standard Inverse IEC_A_STANDARD_INV C1 C2: Very Inverse IEC_B_VERY_INVERSE C2 C3: Extremely Inverse IEC_C_EXTREM_INVERSE C3 C4: Long Time Backup IEC_LONG_TIME_INV C4 CAPE uses a fixed dropout time of 1 cycle; the reset equation is not implemented. The time-dial Common Tap ranges are 0.01 - 15 with step 0.01 for all STYLES, to cover the ranges of both US curves (0.5 to 15) and IEC curves (0.01 to 1.0). Phase TOC elements may be blocked by one of the forward or reverse load-encroachment elements (ZLOUT or ZLIN), or may be supervised by the Zone 2 element M2P. These options are included in the library model.

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2. Increasing the TOC operating time for high currents The SEL-321 has three IOC elements to provide logical outputs for the TOC pickups with no time delay: 51NP, 51QP and 51PP. These have the same torque-control taps as the TOC elements 51N, 51Q and 51P. You may use these to provide a minimum operating time after the TOC element picks up. For the ground TOC element 51N, for example, choose 51NP to supervise an AUX element TX set with the required tripping delay. Use 51N and TX as the contact logic codes for elements 51N and TX. Then set a contact logic expression for the LZOP to include terms (51N AND TX). G. Timers You set all TIMERs using the common taps. (Earlier versions of the SEL-321 library used the TIMER element setting form instead.) For each timer that you intend to include in the trip logic, set a suitable CONTACT_LOGIC_CODE. For instantaneous tripping of a zone, give its TIMER tap an operating time of zero. The phase and ground elements have separate timers, as follows: TIMER Z2PD internal supervisor DIST M2P Zone 2 TIMER Z3PD internal supervisor DIST M3P Zone 3 TIMER Z4PD internal supervisor DIST M4P Zone 4 TIMER Z2GD internal supervisor DIST Z2G Zone 2 TIMER Z3GD internal supervisor DIST Z3G Zone 3 TIMER Z4GD internal supervisor DIST Z4G Zone 4 TIMER 67NL1D internal supervisor IOC 67N1 TIMER 67NL2D internal supervisor IOC 67N2 TIMER 67NL3D internal supervisor IOC 67N3 TIMER 67NL4D internal supervisor IOC 67N4 TIMER 67QL1D internal supervisor IOC 67Q1 TIMER 67QL2D internal supervisor IOC 67Q2 TIMER 67QL3D internal supervisor IOC 67Q3 TIMER 67QL4D internal supervisor IOC 67Q4 TIMER 50PBD internal supervisor VOLT 59PB TIMER 50PRD internal supervisor VOLT 59PR

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The three timers TX, TY and TZ are stored as AUX elements; CAPE automtically sets their pickup and dropout times from the common taps. Other timers are provided for record-keeping only. It is unlikely that they will be included in the LZOP trip path. H. Voltage Elements 27L Phase undervoltage (Min (Va, Vb, Vc)) 3P27 Three-phase undervoltage (Max (Va, Vb, Vc)) 3P59 Three-phase overvoltage (Min (Va, Vb, Vc)) 59L Phase overvoltage (Max (Va, Vb, Vc)) 59N Zero-sequence overvoltage (3V0) 59PB + seq bus overvoltage (Vp) with timer 50PBD Voltage element 59PR, if modeled fully, would need to be a DIST element in CAPE as it operates on both current and voltage. It estimates a remote-bus overvoltage for long lines as (Vo - a1 * Z1L * Ip). The element is not normally used in distance or pilot protection schemes. The CAPE model uses Vp only and treats tap a1 as zero. I. AUX Elements The following AUX elements may be used in the system data with any supervising elements. You must specify the supervisors separately in the system Aux Element Data form for each SEL-321 relay in the system. The pickup and dropout times are read from the common taps specified in the library data. Element Pickup_Time_Tap_Name Dropout_Time_Tap_Name TX TXPU TXDO TY TYPU TYDO TZ TZPU TZDO IV. Distance Element Comparators Let the (+/-/0) sequence relay voltages and currents be (V1, V2, V0) and (I1, I2, I0). Let the phase A, B and C voltages and currents be (Va, Vb, Vc) and (Ia, Ib, Ic). A. Negative-Sequence Directional Elements The relay measures the apparent impedance

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222

VZ = exp(-j MTA)I

The MTA is the tap setting Z1ANG. For forward faults, Z2 is usually negative and must be less than the tap setting Z2F. For reverse faults, Z2 is positive and must be greater than Z2R. For the optimum MTA, the line angle Z1ANG is a good approximation. Abs(I2/I1) must exceed the setting a2, and abs (3*I2) must exceed the pickup 50QF (forward) or 50RF (reverse). B. Supervision of Distance Zones The phase A ground elements will operate only if abs(Ia) > pickup 50L for the zone and abs(3 * I0 > pickup 50G for the zone Each ground distance element is supervised by the negative-sequence directional element, directly in the program code. The B-C phase (MHO) element will operate only if abs(Ib-Ic) > pickup 50AB for the zone. If fewer than three DIST phase loops operate, the phase element is also supervised by the negative-sequence directional element, directly in the program code. If all three phase loops operate, the phase element operation is restricted by the ZLOAD limit as in [1]. C. MHO and QUAD Elements All three phase-phase or phase-ground loops are evaluated; the element asserts if any one phase asserts. In the phase distance elements, a memory-polarized mho comparator evaluates the three phase-phase loops A-B, B-C and C-A. The zone will operate if any one of the three loops operates according to the following equation (shown for loop A-B):

Re V conj V

Re e I conj VZAB AB,MEMjMTA

AB AB,MEMREACH

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