CA1269415A - Distance relay supervision system - Google Patents
Distance relay supervision systemInfo
- Publication number
- CA1269415A CA1269415A CA000498387A CA498387A CA1269415A CA 1269415 A CA1269415 A CA 1269415A CA 000498387 A CA000498387 A CA 000498387A CA 498387 A CA498387 A CA 498387A CA 1269415 A CA1269415 A CA 1269415A
- Authority
- CA
- Canada
- Prior art keywords
- output
- distance
- enable
- distance relay
- sequence
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
- H02H3/32—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors
- H02H3/34—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors of a three-phase system
- H02H3/343—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors of a three-phase system using phase sequence analysers
Landscapes
- Emergency Protection Circuit Devices (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A distance relay system arranged to detect voltage transformer failure and prevent improper operation. A negative sequence segregation network is provided which produces a trans-ient output for 3 phase faults. The transient output is used to enable the distance relay.
A distance relay system arranged to detect voltage transformer failure and prevent improper operation. A negative sequence segregation network is provided which produces a trans-ient output for 3 phase faults. The transient output is used to enable the distance relay.
Description
69)~
C~J-llOg DISTAN~E RELAY SUPERVISION S~STEM
BACKGROUND OF THE INVENTION
This invention relates to distance relaying systems and in particular to relay response to failure of voltage transformers particularly with concurrent maximum loaded situations.
Phase to ground faults and phase to phase faults in - the secondary circuits of voltage transformers used in a distance relaying scheme may result in tripping during normal maximum load in the system. Various schemes have been suggested in the past to detect loss of potential and prevent improper operation of the distance relay. All of the prior schemes however, add a certain time delay and result in a race between the operation ' of the distance relay and the blocking signal which indicated a loss of potential due to voltage transEormer failures. Such prior schemes include comparison with identical voltage sources such as dual secondary voltage transformers or duplicate voltage transformers or comparison of the voltage on both sides of the voltage transformer secondary fuses. A11 such voltage operated schemes however, suffer from some faults and in particular the delay referred to above.
In order to avoid the aforementioned problems involved in attempting to disable the distance relay whenever a VT second-ary fault is detected, an approach may be used which enables the distance relay only if a primary system fault is detected.
One such enabling method would be to AND the output of overcurrent relays with the distance relays. These overcurrent relays must be high speed and set above normal maximum load current. However ~Z~9~
if the system configuration changes the fault current may be below normal maximum load current and the distance relay scheme would fail.
It is therefore necessary that the enabling signal not be present during normal maximum load conditions and yet be reliably present under minimum fault conditions.
SUMMARY OF THE INVENTION
In accordance with the present invention, the enable circuit controlling the operation of the distance relay is derived from zero sequence current and negative sequence current.
A negative sequence segregation network is provided which pro-duces a transient output for 3 phase faults. The output from suitable composite sequence networks provides such transient outputs for any fault. The transient output is used with a pulse stretcher to provide an enable signal to the distance relays. With such an arrangement the distance relays do not respond to normal load current steady state, respond reliably and rapidly to a fault but do not cause improper operation in the presence of a voltage transformer failure. The speed of detection of VT secondary problems is not critical.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic diagram of one embodiment of the invention.
Figure 2 is a second embodiment of the invention.
D~SCRIPTION OF THE PREFERRED EMBODIMENTS
Considering first Figure 1, there is shown a system including system conductors 1, 2 and 3 which carry currents IAIBIC respectively-Current transformers 4, 5 and 6 detect the current in each of the three phases of the system and apply the current to the distance relaying system 7. Current transformers 8, 9 and 10 produce the outputs vA, vB and vC respectively across their load impedance rlr2 and r3. Differential amplifier 11 produces an output va-vb at its output terminal 12. Differential ampli-fier 13 produces an output vb-vc at its output terminal 14.
Inverter amplifier 15 produces an output ~VC at its output terminals 16. Inverter amplifier 17 produces an output ~va at its output terminal 18. The output from terminals 12 and 16 ~;~694~5 is applied across the r/c network comprising capacitor 19 and resistor 20. The output across terminals 14 and 18 is applied across the r/c network comprising capacitor 21 and resistor 22.
The output of terminal 23 of the r/c network 19 and 20 is of the form:
Vx ~ L~. IA2~ 2 ~0 Io The output of terminal 24 is of the form:
Vy ~S~ ~ IB2~ ~ ~
The outputs from terminal 23 ana 24 are applied to a pair of level detectors. When the l~vel of the signal exceeds a pre-determined amount, as determined by the adjustment of the level detector, there is an output from the level which is applied to the l'or" circuit 27. If there is a signal from either of the level detectors 25 or 26 there is an output from the "or" circuit 27 which is applied to the pulse stretcher 28. The output from the pulse stretcher 28 is applied to the enable circuit 29 and the output from the enable circuit is applied to the distance relay.
OPERATION
As will be seen from the foregoing equations, the output at terminal 23 and terminal 24 contains no response to positive sequence current in the steady state. Each will have, however, a transient response. This transient response is variable in polarity depending on the three phase fault initi-ation angle and may be 0. However, the transient output will not be 0 for both terminals 23 and 24 in the presence of the same fault. Any transient output which when applied to level detectors 25 and 26 produces an output from these level detectors in turn produces an output from the "or" circuit 27. This transient cutput is sufficient to trigger the pulse stretcher 28 and cause a pulse of sufficient duration to enable the dis-tance relay. The distance relay can only operate when the suitable enable signal is present. To enable the distance relay 7 to operate in the presence of negative or zero sequence currents, a further input is applied to the enable circuit 29 from terminal 30. This terminal receives a signal representative of a negative or zero sequence current which will enable the distance relay system 7. When the distance relay detects what appears to be ~26~
the fault currents and is in the enable condition it can produce a fault signal on terminal 31.
Considering now Fi~ure 2, this describes an improved system of producing enable signals for the distance relay.
Components identical with those in Figure 1 bear the same designation and the systems conductors 1, 2, 3 as before are carrying currents IAIBIC respectively. Current trans-formers 4, 5 and 6 detect the current in each phase of the system and apply the current to the distance relaying system 7. Current transformers 8, 9 and 10 produce outputs va, Vb, VC respectively across their load impedance. Impedances are rl, r2 and r3.
Differential amplifier 11 produces an output va-vb at its output terminal 12 as before. Dif~erential amplifier produces an output vb~vc at its output terminal as before. The additional differential amplifier 32 produces an output at its terminal 33, vc-va. The output amplifier 15 produces at its output terminal 16 an output -vc. Inverter amplifier 17 produces an output at its terminal 18, ~va. Inverter amplifier 34 produces an output at its terminal 35, -Vb. The output from terminals 12 and 16 is applied to the r/c network comprising capacitor 19 and resistor 20. ~he output from terminals 14 and 18 is applied across r/c network comprising capacitor 21 and resistor 22.
The output across terminals 33 and 35 is applied to the r/c network comprising capacitor 48 and resistor 49. The output at terminal 23 from the r/c network is the form:
Vx ~ 130 I2A~ .5 ~ Io The output at terminal 24 is of the form:
V ~3 ~ I2B~ .5 ~ Io The output at terminal 36 is of the form:
Vz ~3 ~Q I2C~ .5 ~0 Io The outputs from terminals 23, 24 and 36 are applied to inverter amplifiers 37, 38 and 39 and to comparator amplifiers 41, 43 and 45 respectively. Output from terminals 23, 24 and 36 is also applied to comparators 40, 42 and 44 respectively. A reference voltage is applied to terminals 46 and to all the comparators.
When any of the comparators receives Oll its input terminal an input in excess of the reference voltage an output is produced which is applied to the "or" circuit 47. Any signal received by the "or" circuit produces an output which is applied to pulse stretcher 28 as before. The output from pulse stretcher 28 is applied -to the enable circuit 29. The relay can only operate when a suitable enable signal is present. To enable the distance relay 7 to operate in the presence of negative or zero sequence currents a further input is applied to the enable circuit 29 from terminal 30. This terminal receives a signal representative of negative or zero sequence current which would activate the distance relay system. When the distance relay system detects what appears to be fault currents and is in the enabled condition it can produce a fault signal on terminal 31.
The fault signal then can be used to activate a breaker as desired.
It can be seen that the use of zero and negative sequence currents as an enabling signal will make the distance relay immune to power system swings since the currents asso-ciated with such power swings are predominately positive sequence for which the enabling circuit has no steady state response.
C~J-llOg DISTAN~E RELAY SUPERVISION S~STEM
BACKGROUND OF THE INVENTION
This invention relates to distance relaying systems and in particular to relay response to failure of voltage transformers particularly with concurrent maximum loaded situations.
Phase to ground faults and phase to phase faults in - the secondary circuits of voltage transformers used in a distance relaying scheme may result in tripping during normal maximum load in the system. Various schemes have been suggested in the past to detect loss of potential and prevent improper operation of the distance relay. All of the prior schemes however, add a certain time delay and result in a race between the operation ' of the distance relay and the blocking signal which indicated a loss of potential due to voltage transEormer failures. Such prior schemes include comparison with identical voltage sources such as dual secondary voltage transformers or duplicate voltage transformers or comparison of the voltage on both sides of the voltage transformer secondary fuses. A11 such voltage operated schemes however, suffer from some faults and in particular the delay referred to above.
In order to avoid the aforementioned problems involved in attempting to disable the distance relay whenever a VT second-ary fault is detected, an approach may be used which enables the distance relay only if a primary system fault is detected.
One such enabling method would be to AND the output of overcurrent relays with the distance relays. These overcurrent relays must be high speed and set above normal maximum load current. However ~Z~9~
if the system configuration changes the fault current may be below normal maximum load current and the distance relay scheme would fail.
It is therefore necessary that the enabling signal not be present during normal maximum load conditions and yet be reliably present under minimum fault conditions.
SUMMARY OF THE INVENTION
In accordance with the present invention, the enable circuit controlling the operation of the distance relay is derived from zero sequence current and negative sequence current.
A negative sequence segregation network is provided which pro-duces a transient output for 3 phase faults. The output from suitable composite sequence networks provides such transient outputs for any fault. The transient output is used with a pulse stretcher to provide an enable signal to the distance relays. With such an arrangement the distance relays do not respond to normal load current steady state, respond reliably and rapidly to a fault but do not cause improper operation in the presence of a voltage transformer failure. The speed of detection of VT secondary problems is not critical.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic diagram of one embodiment of the invention.
Figure 2 is a second embodiment of the invention.
D~SCRIPTION OF THE PREFERRED EMBODIMENTS
Considering first Figure 1, there is shown a system including system conductors 1, 2 and 3 which carry currents IAIBIC respectively-Current transformers 4, 5 and 6 detect the current in each of the three phases of the system and apply the current to the distance relaying system 7. Current transformers 8, 9 and 10 produce the outputs vA, vB and vC respectively across their load impedance rlr2 and r3. Differential amplifier 11 produces an output va-vb at its output terminal 12. Differential ampli-fier 13 produces an output vb-vc at its output terminal 14.
Inverter amplifier 15 produces an output ~VC at its output terminals 16. Inverter amplifier 17 produces an output ~va at its output terminal 18. The output from terminals 12 and 16 ~;~694~5 is applied across the r/c network comprising capacitor 19 and resistor 20. The output across terminals 14 and 18 is applied across the r/c network comprising capacitor 21 and resistor 22.
The output of terminal 23 of the r/c network 19 and 20 is of the form:
Vx ~ L~. IA2~ 2 ~0 Io The output of terminal 24 is of the form:
Vy ~S~ ~ IB2~ ~ ~
The outputs from terminal 23 ana 24 are applied to a pair of level detectors. When the l~vel of the signal exceeds a pre-determined amount, as determined by the adjustment of the level detector, there is an output from the level which is applied to the l'or" circuit 27. If there is a signal from either of the level detectors 25 or 26 there is an output from the "or" circuit 27 which is applied to the pulse stretcher 28. The output from the pulse stretcher 28 is applied to the enable circuit 29 and the output from the enable circuit is applied to the distance relay.
OPERATION
As will be seen from the foregoing equations, the output at terminal 23 and terminal 24 contains no response to positive sequence current in the steady state. Each will have, however, a transient response. This transient response is variable in polarity depending on the three phase fault initi-ation angle and may be 0. However, the transient output will not be 0 for both terminals 23 and 24 in the presence of the same fault. Any transient output which when applied to level detectors 25 and 26 produces an output from these level detectors in turn produces an output from the "or" circuit 27. This transient cutput is sufficient to trigger the pulse stretcher 28 and cause a pulse of sufficient duration to enable the dis-tance relay. The distance relay can only operate when the suitable enable signal is present. To enable the distance relay 7 to operate in the presence of negative or zero sequence currents, a further input is applied to the enable circuit 29 from terminal 30. This terminal receives a signal representative of a negative or zero sequence current which will enable the distance relay system 7. When the distance relay detects what appears to be ~26~
the fault currents and is in the enable condition it can produce a fault signal on terminal 31.
Considering now Fi~ure 2, this describes an improved system of producing enable signals for the distance relay.
Components identical with those in Figure 1 bear the same designation and the systems conductors 1, 2, 3 as before are carrying currents IAIBIC respectively. Current trans-formers 4, 5 and 6 detect the current in each phase of the system and apply the current to the distance relaying system 7. Current transformers 8, 9 and 10 produce outputs va, Vb, VC respectively across their load impedance. Impedances are rl, r2 and r3.
Differential amplifier 11 produces an output va-vb at its output terminal 12 as before. Dif~erential amplifier produces an output vb~vc at its output terminal as before. The additional differential amplifier 32 produces an output at its terminal 33, vc-va. The output amplifier 15 produces at its output terminal 16 an output -vc. Inverter amplifier 17 produces an output at its terminal 18, ~va. Inverter amplifier 34 produces an output at its terminal 35, -Vb. The output from terminals 12 and 16 is applied to the r/c network comprising capacitor 19 and resistor 20. ~he output from terminals 14 and 18 is applied across r/c network comprising capacitor 21 and resistor 22.
The output across terminals 33 and 35 is applied to the r/c network comprising capacitor 48 and resistor 49. The output at terminal 23 from the r/c network is the form:
Vx ~ 130 I2A~ .5 ~ Io The output at terminal 24 is of the form:
V ~3 ~ I2B~ .5 ~ Io The output at terminal 36 is of the form:
Vz ~3 ~Q I2C~ .5 ~0 Io The outputs from terminals 23, 24 and 36 are applied to inverter amplifiers 37, 38 and 39 and to comparator amplifiers 41, 43 and 45 respectively. Output from terminals 23, 24 and 36 is also applied to comparators 40, 42 and 44 respectively. A reference voltage is applied to terminals 46 and to all the comparators.
When any of the comparators receives Oll its input terminal an input in excess of the reference voltage an output is produced which is applied to the "or" circuit 47. Any signal received by the "or" circuit produces an output which is applied to pulse stretcher 28 as before. The output from pulse stretcher 28 is applied -to the enable circuit 29. The relay can only operate when a suitable enable signal is present. To enable the distance relay 7 to operate in the presence of negative or zero sequence currents a further input is applied to the enable circuit 29 from terminal 30. This terminal receives a signal representative of negative or zero sequence current which would activate the distance relay system. When the distance relay system detects what appears to be fault currents and is in the enabled condition it can produce a fault signal on terminal 31.
The fault signal then can be used to activate a breaker as desired.
It can be seen that the use of zero and negative sequence currents as an enabling signal will make the distance relay immune to power system swings since the currents asso-ciated with such power swings are predominately positive sequence for which the enabling circuit has no steady state response.
Claims (4)
1. In a distance relaying system, means to prevent false operation arising from faults in the system voltage transformer secondary circuits comprising:
means to derive an enable signal representative of sequence fault currents other than positive sequence fault currents;
means to inhibit the operation of the distance relay;
means to enable the operation of the distance relay in response to said enable signal.
means to derive an enable signal representative of sequence fault currents other than positive sequence fault currents;
means to inhibit the operation of the distance relay;
means to enable the operation of the distance relay in response to said enable signal.
2. In a distance relaying system means to prevent false operation arising from faults in the system voltage transformer secondary circuits comprising:
a negative sequence segregation network;
means to derive from said network, a signal repre-sentative of sequence currents other than positive sequence;
means to produce an enable signal from said network;
means to inhibit the operation of the distance relay;
means to enable the operation of the distance relay in response to said enable signal.
a negative sequence segregation network;
means to derive from said network, a signal repre-sentative of sequence currents other than positive sequence;
means to produce an enable signal from said network;
means to inhibit the operation of the distance relay;
means to enable the operation of the distance relay in response to said enable signal.
3. A distance relaying system as claimed in claim 2, wherein said means for producing said enable signal includes means to compare the output from said negative sequence segre-gation network with a reference;
means to produce a first signal in response to out-puts in excess of said reference signal;
means to apply said output to a pulse stretcher and means to derive from said pulse stretcher and enable signal;
means to apply an enable signal to the distance relay to enable the distance relay to operate.
means to produce a first signal in response to out-puts in excess of said reference signal;
means to apply said output to a pulse stretcher and means to derive from said pulse stretcher and enable signal;
means to apply an enable signal to the distance relay to enable the distance relay to operate.
4. In a distance relaying system means to prevent false operation arising from faults in the system voltage transformer secondary circuits comprising:
sequence segregating networks for producing an output representing sequences other than positive sequence current;
comparator means to compare the outputs from said sequence segregating networks with a reference and produce an output when any sequence segregating network output exceeds the reference value;
means to produce an enable signal in respose to said output of sufficient duration to enable the operation of a distance relay.
sequence segregating networks for producing an output representing sequences other than positive sequence current;
comparator means to compare the outputs from said sequence segregating networks with a reference and produce an output when any sequence segregating network output exceeds the reference value;
means to produce an enable signal in respose to said output of sufficient duration to enable the operation of a distance relay.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000498387A CA1269415A (en) | 1985-12-20 | 1985-12-20 | Distance relay supervision system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000498387A CA1269415A (en) | 1985-12-20 | 1985-12-20 | Distance relay supervision system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1269415A true CA1269415A (en) | 1990-05-22 |
Family
ID=4132146
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000498387A Expired CA1269415A (en) | 1985-12-20 | 1985-12-20 | Distance relay supervision system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1269415A (en) |
-
1985
- 1985-12-20 CA CA000498387A patent/CA1269415A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |