2-Winding Transformer: Type HU 3-Winding Transformer: Type HU-1 4-Winding Transformer: Type HU-4 4-Circuit Bus: Type HU-4

Transcription

1 Westinghose Application Types HU, HU1, and HU4 relays are high speed differential nits with two, three, or for restraint circits respectively; all incorporating a harmonic restraint circit to prevent false tripping on magnetizing inrsh crrents associated with transformer energization. All are designed with a variable ratio characteristic which provides high sensitivity at low crrent magnitdes with an increase in percentage ratio at higher crrents. Each of the relays then, will detect light internal falts within the transformer and, at the same time, prevent false tripping on heavy external falt crrents which may case variation in the crrent transformer performance at high crrents. This is particlarly desirable when severe satration of crrent transformers occrs de to the de component of asymmetrical short circits. The harmonic restraint featre of these relays prevents false tripping on magnetizing inrsh crrents which appear at the relay as an internal falt. Sch inrsh crrents are rich in harmonics, with the second harmonic being predominant. Since this second harmonic is always present in magnetizing inrsh crrents and not in internal falt crrent waves the harmonic restraint nit will not close its contacts nless second harmonic content is less than 15 percent of the fndamental. Normal application of these relays is: 2Winding : Type HU 3Winding : Type HU1 4Winding : Type HU4 4Circit Bs: Type HU4 The HU relay has two restraint transformers and is for se with 2winding transformer protection. The HU1 has a third restraint transformer and is sed for three winding application. The HU4 has for restraint Descriptive Blletin Page 1 Types HU, HU1, HU4 Relays Single Phase nstantaneos Variable Percentage circits, and may be applied to threewinding transformers with a tertiary winding, or a transformer and bs section combination. The Type HU4 may be applied to any bs circit where the external falt crrent throgh the bs is twenty times tap vale secondary crrent or lesse.g., 1 amperes on the 5 ampere tap. Occasionally an axiliary crrent balance transformer is sed on the line side of the power transformer to adjst the crrent transformer secondary crrents to the bs sections inclded in the protected zone. Taps are spplied to compensate for main crrent transformer mismatch. The relays are available with a sensitivity of either.3 or.35 times tap setting. The 3% sensitivity relay satisfactorily handles p to 15% mismatch (e.g., ±1 % transformer tap changing, pls 5% crrent transformer mismatch). The 35% nit handles p to 2% mismatch. See Figres 4, 5, 9, and 1. Janary, 1974 Spersedes DB 41347, dated March E. D. C/215/DB

2 Descriptive Blletin Page 2 Westinghose Featres 1. High secrity de to variable ratio characteristic The relay detects light internal falts within the transformer and at the same time prevents false tripping on heavy external falts which may case variation in the crrent transformer performance at high crrents. 2. Fast operating speed limits falt damage to the protected transformer. With the contining trend toward larger and more costly power transformers, the ser is best sited to apply protective relays offering the fastest operating speeds. 3. Greater secrity dring external falts Falts external to the transformer prodce large magnitde throgh crrents which case nsymmetrical satration to the crrent transformers on each side of the power transformer. The higher designed brden of the HU relay's operating coil forces the strong CT on one side of protected power transformer to more effectively spport the weak CT on the other side as desired for secre operation. 4. Second harmonic filter circits are sed to prevent false tripping of the relays dring magnetizing inrsh crrent at startp The HU relays se the filtered inpt for the instantaneos nit as well as the main differential nit. Therefore, the instantaneos nit can be set more sensitively, still being secre from false trips de to second harmonic inrsh. 5. The type HU relays are designed thermally to allow crrents of 2.5 to 3.4 times tap vale. 5 Protected (a) External Falt Operation External Falt Conditions With the relay connected as shown in Figre 3a, external falt crrents will flow in the restraint transformers of the differential nit. f the line crrent transformers are below satration and with correct tap settings, no effective crrent flows in the operating transformer of the relay. Hence, a contact opening torqe is prodced in the differential polar nit. On heavy external falts where a main transformer satrates, crrent will flow in the operating circit of the relay. Under these conditions the harmonic restraint nit may close its contacts depending on the harmonics present in the false operating crrent. Operation of the differential nit is prevented by its variable percentage characteristic, since a large differential crrent is reqired to close the contacts dring heavy external falts. nternal Falt Conditions On internal falts the restraint of the differential nit is proportional to the largest restraint crrent flowing. The sm of the two restraint crrents flows into the operating transformer, prodcing an excess of operating torqe, and the differential nit operates. (See Figre 3b.) f the internal falt is fed from one sorce only, the falt crrent flows in one restraint transformer and the operating transformer. An excess of operating torqe is again prodced to operate the differential nit. On heavy internal falts, the nstantaneos ndicating Trip Unit will operate before the main differential nit. Since this nit is connected to an air gap transformer, essentially only the sine wave component of an internal falt is applied to the lit nit. The de component is bypassed by the transformer primary. For example, an internal falt with a first peak of 28 times tap vale (5% de component) is redced to 14 times tap vale (de component absent) in the transformer secondary. As the lit nit is set to operate at 1 times rms tap vale, it will jst operate nder these conditions. The varistor is connected across the de side of the restraint rectifier of the harmonic restraint nit to prevent excessive voltage peaks from appearing across the rectifiers cased by transformer action of the polar nit coils dring heavy internal falts. When a magnetizing inrsh wave is applied to the relay, the de component of the wave is bypassed by the air gap operating transformer. The other components of the inrsh wave are fed into the filter circits. The block and pass characteristics of the filter circits feed the second harmonic component of the wave into the restraint coil of the polar nit, and the other components into the operating coil. The polar nit will not close its contacts nless the second harmonic content is less than 15% of the fndamental component. The ndicating nstantaneos Trip will not operate on inrsh. Protected 15 (b) nternal Falt Fig. 3: HU4 simplified external connections showing crrent distribtion for external and internal falts. nternal Falt

3 , Characteristics Single phase, 6 hertz, spstcc contacts Operating Time See Figre 6. Restraint Circits Two in HU, three in HU1, 4 in HU4; pls one harmonic restraint and one operating circit in each. Ratio Taps 2.9, 3.2, 3.5, 3.8, 4.2, 4.6, 5., 8.7 amperes. Variable Percentage Characteristics HU, HU1: See Figres 8 and 1 Minimm Trip 3% or 35% of tap vale. Performance See Figres 6 and 7. Relay Settings Select the ratio in matching taps. No other settings are reqired. To calclate the reqired tap settings and check crrent transformer performance, follow the steps otlined on pages of Application Data The HU4 relay is applicable to circits where the crrent transformer ratio error is 1 % or less with maximm symmetrical external falt crrent flowing, or with eight times relay tap crrent flowing. Taps are provided in the relay restraint and operating circits to compensate for main crrent transformer mismatch. These taps are rated in terms of secondary amperes with the ratings mentioned nder Ratio Taps. Effective nbalance shold not exceed the vales indicated by the 15% mismatch crve, Figre 4, or 2% mismatch crve, Figre 5. Sensitivity Relays are available with either.3 or.35 times tap rating. The 3% sensitivity relay will accommodate p to 15% mismatch; and the 35% nit will handle as mch as 2% mismatch. See Figre 8 for comparison of the 3% and 35% sensitivity. Energy Reqirements l:ontinos P Angle T, Rating (i) _ Each Restraint Circit ap Operating Circit CD Degrees crrent lags voltage at tap vale crrent. Voltage taken with Rectox type voltmeter. 23 ndicating Contactor Switch (CS) Has.2 and 2. ampere taps. Will close 3 amperes and carry this long enogh to trip circit breaker. ndicating nstantaneos Trio (lit) HU, HU1 Set to operate at 1 times rms tap vale. Will close 3 amperes and carry long enogh to trip a circit breaker. HU4 Set to operate at 15 times rms tap vale. Will close 3 amperes and carry long enogh to trip a circit breaker. Thermal Capability Onesecond thermal rating: 3 amperes. Thermal capacities for short times other than one second may be calclated on the basis of time being inversely proportional to the sqare of the crrent. Descriptive Blletin Page 3 Types HU, HU1, HU4 Relays Single Phase nstantaneos Variable Percentage VoltAmperes At Tap Vale Times Tap Vale Times Tap Vale

4 .. Descriptive Blletin Page 4 Westinghose Differential Voltage Characteristic With Pickp of.3 Times Tap 6..s 5. ;;; a: :; 4. ' c: 3. t <(!) 2. > <(! ' 1. E ;c <( Fig Larger Restraint Crrent in Mltiples of Tap Vale Crrent Operating Time Crve (6 Hz Base) = E i= ' c: Fig ating Crrent in Mltiples of Tap Vale Crrent Differential Voltage Characteristic With Pickp of.35 Times Tap ' = <( > <(! ' E ;c <( Fig. 5 Larger Restraint Crrent in Mltiples of Tap Vale Crrent Freqency Response Crve '.!::! 4 a.. t: 3 ' ' '::,2 c: c3 1 ' ii: Fig. 7 Freqency in Hertz

5 Comparison of the Differential Characteristic of HU and HU1 Differential Unit With Pickps of.3 And.35 Times Tap.:: C> ;; Fig. 8 Larger Restraint Crrent in Mltiples of Tap Vale Crrent Typical Differential Characteristic of HU4 Differential Unit ' > 12 ' 1 1., :E 8 :i! 6 4 C> 2 '.:: Larger Restraint Crrent in Mltiples of Tap Vale Crrent Fig Descriptive Blletin Page 5 Types HU, HU1, HU4 Relays Single Phase nstantaneos Variable Percentage Typical Differential Characteristic of HU and HU1 Differential Unit ' 1., :E :i! C> Fig Larger Restraint Crrent in Mltiples of Tap Vale Crrent 4715

6 Descriptive Blletin Page 6 Westinghose External Wiring HU, HU1 Relays, WyeWye Delta Bank Fig. 11 Device Nmber Chart 43Trip Ctoff Switch 86Type WL Axiliary Tripping Relay Type HU or HU1 Differential Relay DUDifferential Unit DOperating Coil ARestraint Coil R,} R2 Throgh Restraint s R3 HRUHarmonic Restraint Unit perating Coil ARestraint Coil CSndicating Contactor Switch litndicating nstantaneos Trip Power A 2 3 rte.+111' 1 B c r Connect,ons r+ With HU1 Only 'Cf1l ; N >2 : : i 3 1

7 1 Phase Coil R, Circits R2 R3 HU1 Used With Only, 5 Phase 2 (Same as PH. 1) L..+ca= C@E(;!..;:,., :iidu 6 HU Cy. Block 12 Cy. Pass Filter Cod CircUits PH. 1) Phase 2 (Same as, 5 PH. 1) Phase 3 (Same as Phase 3 Coil Circits PH. 1) Phase 3 (Same as Descriptive Blletin Page 7 Types HU, HU1, HU4 Relays Single Phase nstantaneos Variable Percentage D.C. Trip Bs Pos. Phase 2 and 3 Connected Same as Phase 1 47C536 Sb.5

8 Descriptive Blletin Page 8 Westinghose External Wiring HU4 Relay WyeWye Delta Bank Device Nmber Chart 43Trip Ctoff Switch 86Type WL Axiliary Tripping Relay Type HU4 DUDifferential Unit perating Coil RRestraint Coil R,} R2 Throgh Restraint s Rs Fig. 12 HRUHarmonic Restraint Unit perating Coil RRestraint Coil CSndicating Contactor Switch lit ndicating nstantaneos Trip 2 3 V\ r L Power. 52 High Side ntermediate Low Side n [Ylfl A B c r 52 ' ),, 1 3 l 1 T 2 J l A ;;; 3

9 HU,., 52 L f LJ '' <11 <11 1' HRU 1 :_ R, R, !) l ;) < R R3 o Phase 1 ;f f ff Phase 2 (Same as PH. 1) s Phase 1 Coil Circits R R2 ($)o 6 Hz. Block 12 Hz. Pass Filter )13 ( Phase 3 (Same as PH. 1) 9 13 f j12 Descriptive Blletin Page 9 Types HU, HU1, HU4 Relays Single Phase nstantaneos Variable Percentage 'T rt' D.C. Trip Bs CS DU 1 43!' Neg. _ Phase 2 and 3 Connected Same as Phase

10 Descriptive Blletin Page 1 Westinghose nternal Wiring, HURelay, Dpstcc Contacts, FT 31 Case (front View) Fig. 13 Second Harmonic Block Circit ndicating Contactor Switch / ' Ln JCS J JHRU1 RU CS oi :ro ' \ T n 1 6:irY+ fv fv fv r (' (' '( OV'. v &J 9 i 9 \A!. gjr r ) > r L_ ' tlt>< > Note: Terminals 346 are to be Jmped at Relay Case Terminal 5 Top 3 5 Tap Connection 7 Middle ' ndicating nstantaneos Trip (lit) Fndamental Block Second Harmonic Pass Circit Harmonic Restraint Unit (HRU) Top Varistor Operating Harmonic Restraint Unit Operating Differential Unit Differential Unit (DU) Bottom Throgh Restraint Chassis Operated Shorting Switch, 4 Flexitest Switch, _..J _9 9 ( 7 1 Case Terminals Crrent Test Jack 185A36 Sb.2

11 nternal Wiring, HU1 Relay, Dpstcc Contacts, FT31 Case (Front View) Fig. 14 Second Harmonic +.. Block Circit ndicating Contactor Switch ++{ Note: Terminals 3468 are to be Jmped at Relay Case Terminal 5 Top Tap Connection 7 Middle 9 Bottom Descriptive Blletin Page 11 Types HU, HU1, HU4 Relays Single Phase nstantaneos Variable Percentage ndicating nstantaneos Trip (lit) Fndamental Block Second Harmonic Pass Circit Varistor '++ Differential Unit (DU) Bottom ++ Throgh Restraint Chassis Operated,++if Shorting Switch Flexitest Switch 185A37 Sb.2

12 Descriptive Blletin Page 12 Types HU, HU1, HU4 Relays Single Phase nstantaneos Variable Percentage nternal Wiring, HU4 Relay, Dpstcc Contacts, With Second Harmonic Restraint, FT42 Case (Front View) ndicating nstantaneos Trip (lit) =======:;:;=====:J.==========j:::;+ Fndamental Block r ndicating Contact Switch 1+( Tap Terminal Connection 13 Upper 5 2nd 7 3rd 9 Bottom Note: Terminals Are to be Jmped at Relay Case Fig. 15 Frther nformation Prices and Ordering nformation: PL 412 Flexitest Case: DB Application Data: AD 41 3 General nstrctions: HU and HU1: L /HU4; L Other Protective Relays: SG 41 Westinghose Electric Corporation Relaynstrment Division: Newark Plant, Newark, N.J. 711 Printed in U.S.A. Second Harmonic Pass Circit '+1 Differential Unit (DU) Bottom +Flexitest Switch '+ Crrent Test Jack ' Case Terminals 188A542 Sb 4

13 Jly, 1988 Spersedes DB 41347, pages 112, dated Janary, 1974 Mailed to: E, D, C/414B Application Types HU, HU1, and HU4 relays are high speed differential nits with two, three, or for restraint circits respectively; all incorporating a harmonic restraint circit to prevent false tripping on magnetizing inrsh crrents associated with transformer energization. All are designed with a variable ratio characteristic which provides high sensitivity at low crrent magnitdes with an increase in percentage ratio at higher crrents. Each of the relays then, will detect light internal falts within the transformer and, at the same time, prevent false tripping on heavy external falt crrents which may case variation in the crrent transformer performance at high crrents. This is particlarly desirable when severe satration of crrent transformers occrs de to the de component of asymmetrical short circits. Westinghose Electric Corporation Relay and Telecommnications Division Coral Springs, FL 3365 Figre 1 Tap Block ndicating nstantaneos,..:l31j!! Trip The harmonic restraint featre of these relays prevents false tripping on magnetizing inrsh crrents which appear at the relay as an internal falt. Sch inrsh crrents are rich in harmonics, with the second harmonic being predominant. Since this second harmonic is always present in magnetizing inrsh crrents and not in internal falt crrent waves the harmonic restraint nit will not close its contacts nless second harmonic content is less than 15 percent of the fndamental. Normal application of these relays is: 2Winding : Type HU 3Winding : Type HU1 4Winding : Type HU4 4Circit Bs: Type HU4 The HU relay has two restraint transformers and is for se with 2winding transformer protection. The HU1 has a third restraint transformer and is sed for three winding application. The HU4 has for restraint cir Descriptive Blletin Page 1 Single Phase nstantaneos Variable Percentage Relays Types HU, HU1, HU4 }Harmonic Figre 2 Restraint Unit ndicating Contactor Switch cits, and may be applied to threewinding transformers with a tertiary winding, or a transformer and bs section combination. The Type HU4 may be applied to any bs circit where the external falt crrent throgh the bs is twenty times tap vale secondary crrent or lesse.g., 1 amperes on the 5 ampere tap. Occasionally an axiliary crrent balance transformer is sed on the line side of the power transformer to adjst the crrent transformer secondary crrents to the bs sections inclded in the protected zone. Taps are spplied to compensate for main crrent transformer mismatch. The relays are available with a sensitivity of either.3 or.35 times tap setting. The 3% sensitivity relay satisfactorily handles p to 15% mismatch (e.g., ± 1% transformer tap changing, pls 5% crrent transformer mismatch). The 35% nit handles p to 2% mismatch. See Figres 4, 5, 9, and 1.

14 Descriptive Blletin Page 2 Featres 1. High secrity de to variable ratio characteristic The relay detects light internal falts with the transformer and at the same time prevents false tripping on heavy external falts which may case variation in the crrent transformer performance at high crrents. 2. Fast operating speed limits falt damage to the protected transformer. With the contining trend toward larger and more costly power transformers, the ser is best sited to apply protective relays offering the fastest operating speeds. 3. Greater secrity dring external falts Falts external to the transformer prodce large magnitde throgh crrents which case nsymmetrical satration to the crrent transformers on each side of the power transformer. The higher designed brden of the HU relay's operating coil forces the strong CT on one side of protected power transformer to more effectively spport the weak CT on the other side as desired for secre operation. 4. Second harmonic filter circits are sed to prevent false tripping of the relays dring magnetizing inrsh crrent at startp The HU relays se the filtered inpt for the instantaneos nit as well as the main differential nit. Therefore, the instantaneos nit can be set more sensitively, still being secre from false trips de to second harmonic inrsh. 5. The type HU relays are designed thermally to allow crrents of 2.5 to 3.4 times tap vale. Protected (a) External Falt Operation External Falt Conditions With the relay connected as shown in Figre 3a, external falt crrents will flow in the restraint transformers of the differential nit. f the line crrent transformers are below satration and with correct tap settings, no effective crrent flows in the operating transformer of the relay. Hence, a contact opening torqe is prodced in the differential polar nit. On heavy external falts where a main transformer satrates, crrent will flow in the operating circit of the relay. Under these conditions the harmonic restraint nit may close its contacts depending on the harmonics present in the false operating crrent. Operation of the differential nit is prevented by its variable percentage characteristic, since a large differential crrent is reqired to close the contacts dring heavy external falts. nternal Falt Conditions On internal falts the restraint of the differential nit is proportional to the largest restraint crrent flowing. The sm of the two restraint crrents flows into the operating transformer, prodcing an excess of operating torqe, and the differential nit operates. (See Figre 3b.) f the internal falt is fed from one sorce only, the falt crrent flows in one restraint transformer and the operating transformer. An excess of operating torqe is again prodced to operate the differential nit. Figre 3: HU4 simplified external connections showing crrent distribtion for external and internal falts. On heavy internal falts, the nstantaneos ndicating Trip Unit will operate before the main differential nit. Since this nit is connected to an air gap transformer, essentially only the sine wave component of an internal falt is applied to the lit nit. The de component is bypassed by the transformer primary. For example, an internal falt with a first peak of 28 times tap vale (5% de component) is redced to 14 times tap vale (de component absent) in the transformer secondary. As the lit nit is set to operate at 1 times rms tap vale, it will jst operate nder these conditions. The varistor is connected across the de side of the restraint rectifier of the harmonic restraint nit to prevent excessive voltage peaks from appearing across the rectifiers cased by transformer action of the polar nit coils dring heavy internal falts. When a magnetizing inrsh wave is applied to the relay, the de component of the wave is bypassed by the air gap operating transformer. The other components of the inrsh wave are fed into the filter circits. The block and pass characteristics of the filcer circits feed the second harmonic component of the wave into the restraint coil of the polar nit, and the other components into the operating coil. The polar nit will not close its contacts nless the second harmonic content is less than 15% of the fndamental component. The ndicating nstantaneos Trip will not operate on inrsh. Protected (b) nternal Falt nternal Falt Jly, 1988