GE Multilin 1

PVDPVDDifferential Voltage

High speed differential protection for

busses and feeders for use with

standard bushing-type current

Features and Benefits

� Replacement for earlier PVD models

� Thyrite stacks limit potential voltage acrossrelay

� Drawout case construction

Applications

� Bus differential high z voltage

� Shunt reactor differential protection

� Transformer high z ground differential

Protection and Control

� High-speed, high z voltage sensing

� High seismic instantaneous O/C unit

� Breaker failure protection (with suitable timing relay)

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PVD Differential Voltage

IntroductionThe PVD21 relay is a single-phase, high-speed,high-impedance, voltage-operat-ed relay designed to provideprotection in bus differentialschemes. The PVD21 utilizes thesame operating principle (highimpedance voltage) as the earlierPVD models, but provides fasteroperating speeds and higher seis-mic capabilities. Typical operatingspeed is 20 ms at 4X pickup (SeeFig. 1). The PVD21 is mechanicallyinterchangeable with the earlierPVD21 models, and providesadditional output contacts asshown in Figs. 2 and 3.

DescriptionThe PVD21 relay is available infour models. All models include ahigh-speed voltage sensing unit(87L) that operates from the volt-age provided by the differentiallyconnected CT’s during an internalfault. In addition, a high seismicinstantaneous overcurrent unit(87H) is included in the PVD21Band 21D models The overcurrentunit 87H, which has an electricallyseparate output contact, may beused to supplement the voltage

unit 87L, and/or to implementbreaker failure protection whenused with a suitable timing relayand other auxiliary devices.

The PVD21A and 21B models usea single Thyrite® stack to limit themagnitude of the voltage devel-oped across the relay. Forapplications where high internalfault currents can be encoun-tered, the PVD21C and 21Dmodels are available. Theserelays include two Thyrite stacks,and offer the same basic protec-tion, but with a slight decrease insensitivity. See the PVD21instruction book for proper selec-tion and application for thePVD21C and 21D models.

Current TransformerRequirementsThe PVD21 relays can be appliedfor bus protection in most caseswhere CT’s having negligibleleakage reactance are used. Thisgenerally includes any kind ofcurrent transformer with atoroidal core if the windings (onthe taps used) are completelydistributed about the core. It ispreferable that all the CT’s in thebus differential circuit have the

same ratio. When adding to anexisting bus, at least one CT setin the new breaker should beordered with the same ratio asthe bus differential CT’s in theexisting breakers. If the differen-tial circuit unavoidably includesdifferent ratio CT’s, application ofthe PVD21 may still be possible,but special attention must begiven to protection against over-voltage conditions during internalfaults. Refer applications involv-ing different ratio CT’s to the localGeneral Electric Company salesoffice.

8

7

6

53

Shorting bar

12

87L

87L

87L

Used withPVD21C

S.I.

S.I.

S.I.

Input to 87Lcircuitry

* * * * *

*

= Voltage-operated unit= Seal-in unit= Short finger

Connection DiagramFig. 2. Simplified internal connection diagram for PVD21A and PVD21C

8

7

6

53

Shorting bar

12

87L

87L

87LUsed withPVD21D

S.I.

S.I.

S.I.

Input to 87Lcircuitry

* * * * *

10

9

87H

87H

87H

* *

*

= Voltage-operated unit= Overcurrent unit= Seal-in unit= Short finger

4

Fig. 3. Simplified internal connection diagram for PVD21B and PVD21D

RatingsThe voltage unit 87L has a contin-uous rating of 150 V.

The current unit 87H is a Hi-G,high seismic instantaneous unitwith the following ratings for thecoil:

87H UNIT (2-50 A RANGE)

Continuous One SecLink Range Rating RatingPosition (A) (A) (A)

Low 2-10 3.7High 10-50 7.5

130

The contacts of the 87L unit havea current closing rating of 30 Afor voltages not exceeding 250 V.The current carrying rating islimited by the seal-in unit rating(see below). The target and seal-in unit is a Hi-G, high seismicunit, dual rated with 0.2 and 2.0 A(dc) taps, with the followingratings:

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5

PVD Differential Voltage

3

SELECTION GUIDE Single-phase (3 Required)

150

605060506050 60 5060

75V 500V

- - -- - -2A2A- - -- - -2A2A4A

- - -- - -50A50A- - -- - -50A50A100A 2

PVD21A1AA2A

PVD21B1AB2A

PVD21C1AC2A

PVD21D1AD2A

PVD21D3A

M1 20(9) 27( 1 2.2)

ContinuousRating

(V)Frequency

(Hz) Min Max Min MaxThyrite®

StacksModel

NumberCaseSize Net Ship

NOTE: All PVD relays include a 0.2/2.0 A T. & SI Unit used in conjunction with the 87L Unit.

Voltage Unit(87L)

Current Unit(87H)

Approx. Wt.in lbs (kg)

}}

1

2

DC resistance (Ohms)Minimum operating (A)Carry continuous (A)Carry 30 A for (sec)Carry 10 A for (sec)

8.00.20.30.03 0.25

0.24 2.03430

DescriptionTap Setting

0.2 A 2.0 A

Fig. 1. Typical operating times of the PVD relay—87L unit

30

20

10

00 2 3 4 5 6

Multilples of pickup setting

Pic

kup

tim

e in

mill

isec

on

ds

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