Distance Relay Modeling Discussion

WECC MVWG MeetingMay 2018

Bill Price

GE Energy Consulting

Distance Relay Models – What’s the issue?

How to get correct operation for multi-section, series comp. lines, particularly for generic relay models: lnrelscan, zlinw

• Example:

R = 0.0067, X = 0.088

B = 7.84

From BusLine Connected

Shunt Reactor Bypass

- manual

- gap

- MOV

X = - 0.019 X = - 0.019

To Bus

B / 2 B / 2

Bsh 1

Bsh 2

• Where should Zapp be measured? (May differ depending on relaying scheme.)• Include / exclude series capacitors?• Include / exclude line-connected shunt reactors?

• For generic relays:• What impedance should be used to determine relay zone reach?

• Is simple stepped-zone scheme adequate? (No)• Relay schemes for series-comp. lines are complicated – can something reasonable be achieved

with just a distance relay model?

Currently in PSLF

• Relays applied to multi-section lines:• Zapp can only be measured at the bus – includes series caps and shunt reactors• Generic relays use net line impedance to determine zone reach

• If line is represented by separate single-section branches:• Relay can be applied to branch that is the actual line to exclude series cap• Generic relays will be applied to each branch separately• Only the faulted branch will be tripped.

Another example:

From Bus To Bus

B / 2B / 2

Bsh

= -0.545

X = 0.0614

B = 1.139

X = -0.02004 X = 0.003X = 0.04856

B = 1.0768

X = -0.0242

Bsh

= -0.545Bsh

= -0.545

PSLF Distance Relays

Individual Distance Relays

WECC Distance Relay – DISTREL, ZONEDEF, BLINDEF, RELODEN• 4 zones with circle, lens, tomato, quadrilateral shapes (in ohms)

• Can include blinders and load encroachment protection

• Includes simple transfer tripping (DUTT) and reclosing

• No special provision for multi-section lines (e.g. Zapp location)

• Other transfer trip schemes not currently implemented

ZLIN family• ZLIN1 – 3 circular zones only; tapped lines (radial only)

• ZLIN2 – same as ZLIN1 but permits non-radial taps

• ZQLIN1 – same as ZLIN1 but permits lens, tomato, quadrilateral zones

• ZQLIN2 – same as ZQLIN1 but permits non-radial taps

• ZPOTT – like ZQLIN1 but with Permissive Overreaching Transfer Trip

• ZDCB – like ZQLIN1 but with Directional Comparison Blocking

PSLF Distance Relays

Generic Distance Relays

WECC Generic Relay - LNRELSCAN• 3 circular zones – fractions of line X

• No special provision for multi-section lines

– Zapp measurement location

– Line X to use for zone reach

– Probably not critical since it’s only for scanning unfaulted lines

ZLINW• 2 circular zones – fractions of line X

• No special provision for multi-section lines

– Zapp measurement location

– Line X to use for zone reach

• Reasonably accurate model required for DCAT project

PSLF Distance Relays

ZLIN Limitations• Can’t exclude line shunt from Zapp

• Can’t specify location of Zapp measurements (problem for series- compensated multi-section lines)

• Limited transfer tripping capability (ZPOTT and ZDCB models only)

• ZLINW limited to 2 zones; no pickup time delay for zone 1

R = 0.0067, X = 0.088

B = 7.84

From BusLine Connected

Shunt Reactor Bypass

- manual

- gap

- MOV

X = - 0.019 X = - 0.019

To Bus

B / 2 B / 2

Bsh 1

Bsh 2

PSLF Distance Relays

Proposed ZLIN replacement (for individual line) – ZLINETT(?)• Include all features of ZLIN1, ZLIN2, ZQLIN1, ZQLIN2

• Option to exclude near-end line-connected shunts from Zapp

• Option for Zapp location for series-comp. lines (at bus or after cap)

• Options for transfer tripping (add comm. delay parameter):

– No transfer trip – separate relays at each end of line

– No transfer trip, but use same relay zones at both ends

– Direct Under-reaching Transfer Trip (DUTT)

– Permissive Under-reaching Transfer Trip (PUTT)

– Permissive Over-reaching Transfer Trip (POTT)

– Directional Comparison Blocking with Transfer Trip (DCBTT)

• Perhaps, change zone definition parameters to agree with WECC ZONEDEF (but with Z in p.u. or option for ohms/p.u.)

• Add automatic reclosing

• Add blinders (for zone 3)

PSLF Distance Relays

Suggested changes for DISTREL (WECC) model • Option to exclude near-end line-connected shunts from Zapp

• For multi-section lines:

– Option for Zapp location for series-comp. lines (at bus or after cap)

• Options for transfer tripping (add comm. delay parameter):

– No transfer trip – separate relays at each end of line

– No transfer trip, but use same relay zones at both ends

– Direct Under-reaching Transfer Trip (DUTT)

– Permissive Under-reaching Transfer Trip (PUTT)

– Permissive Over-reaching Transfer Trip (POTT)

– Directional Comparison Blocking with Transfer Trip (DCBTT)

PSLF Generic Distance Relay

ZLINW2 model – under development• 3 zones with pickup delay for each zone

• Exclude near-end line-connected shunts from Zapp

• Measure Zapp on line-side of initial series capacitor, if any

• Apply reach fractions to total line X excluding initial capacitor, if any

• Enable or disable transfer trip (with comm. delay)

Side benefit – capability to get V at nodes of multi-section line

From Bus To Bus

B / 2B / 2

Bsh

= -0.545

Zapp = V / I

X = 0.0614

B = 1.139

X = -0.02004 X = 0.003X = 0.04856

B = 1.0768

X = -0.0242

Bsh

= -0.545Bsh

= -0.545

Zapp = V / I