The “Sudden change in current variation” function is a fast way of finding any abnormality in line currents. When there is a fault in the system, the current changes faster than the voltage. SCCVPTOC finds abnormal condition based on phase-to-phase current variation. The main application is as a local criterion to increase security when transfer trips are used.

For more detailed information on “Sudden change in current variation” function, refer to ABB, Relion 670 Series manuals.

The “Compensated over and undervoltage protection” function calculates the remote end voltage of the transmission line utilizing local measured voltage, current and with the help of transmission line parameters, that is, line resistance, reactance, capacitance and local shunt reactor. For protection of long transmission line for in zone faults, COUVGAPC can be incorporated with local criteria within direct transfer trip logic to ensure tripping of the line only under abnormal conditions.

For more detailed information on “Compensated over and undervoltage protection” function, refer to ABB, Relion 670 Series manuals.

The “Low active power and power factor protection” function measures power flow. It can be used for protection and monitoring of phase wise low active power, phase wise low power factor and phase wise reactive power and apparent power as service values.

For more detailed information on “Low active power and power factor protection” function, refer to ABB, Relion 670 Series manuals.

“Analog inputs” (input channels) must be configured and set properly in order to get correct measurement results and correct protection operations. For power measuring, all directional and differential functions, the directions of the input currents must be defined in order to reflect the way the current transformers are installed/connected in the field ( primary and secondary connections ). Measuring and protection algorithms in the IED use primary system quantities. Setting values are in primary quantities as well and it is important to set the data about the connected current and voltage transformers properly.

For more detailed information on “Analog inputs”, refer to ABB, Relion 670 Series manuals.

The “Frequency time accumulation protection” for generator protection provides the START output for a particular settable frequency limit, when the system frequency falls in that settable frequency band limit and positive sequence voltage within settable voltage band limit. The START signal triggers the individual event timer, which is the continuous time spent within the given frequency band, and the accumulation timer, which is the cumulative time spent within the given frequency band.

For more detailed information on “Frequency time accumulation protection” function, refer to ABB, Relion 670 Series manuals.

By the “100% Stator earth fault protection, 3rd harmonic based” either the 3rd harmonic voltage differential principle, the neutral point 3rd harmonic undervoltage principle or the terminal side 3rd harmonic overvoltage principle can be applied. However, differential principle is strongly recommended. Combination of these two measuring principles provides coverage for entire stator winding against earth faults.

For more detailed information on “100% Stator earth fault protection, 3rd harmonic based” function, refer to ABB, Relion 670 Series manuals.

The “Voltage unbalance protection of shunt capacitor bank” function uses the neutral voltage measurement of an ungrounded single or double WYE configuration of SCB. The protection arrangements are based on the terminal voltage limit and the current limit of the capacitor units.

For more detailed information on “Voltage unbalance protection of shunt capacitor bank” function, refer to ABB, Relion 670 Series manuals.

Voltage
unbalance protection of the shunt capacitor bank

SCUVPTOV

Uub >

60V

Signals & Setting Parameters

SCUVPTOV function block

SCUVPTOV Input signals

SCUVPTOV Input signals

Name

Type

Default

Description

U3P

GROUP SIGNAL

–

Group signal for three phase bus voltage

U3NEUT

GROUP SIGNAL

–

Group signal for capacitor bank neutral
voltage

BLOCK

BOOLEAN

0

Block of function

BLKTR

BOOLEAN

0

Block of trip

BLKALM

BOOLEAN

0

Block of alarm

BLKWRN

BOOLEAN

0

Block of warning

INHIBIT

BOOLEAN

0

Inhibit the function

TRIGCOMP

BOOLEAN

0

Trigger input to store the calculated
compensation factors into the IED memory. The stored values will be used for
future compensation in the function.

RESETCOMP

BOOLEAN

0

Force the stored compensation factors to
zero.

SCUVPTOV Output signals

SCUVPTOV Output signals

Name

Type

Description

TRIP

BOOLEAN

Trip signal

START

BOOLEAN

Start signal

ALARM

BOOLEAN

Alarm signal

WARNING

BOOLEAN

Warning signal

BLKD

BOOLEAN

Block due to bus voltage in any phase is lower than the set
UMin> value or SCB disconnection is detected

COMPEXED

BOOLEAN

Indicates that a trigger was made for compensation

PUNUNBAL

REAL

Capacitor bank neutral unbalance voltage in % of UBase

SCUVPTOV Non group settings (basic)

SCUVPTOV Non group settings (basic)

Name

Values (Range)

Unit

Step

Default

Description

GlobalBaseSel

1 – 12

–

1

1

Selection of one
of the Global Base Value groups

SCUVPTOV Group settings (basic)

SCUVPTOV Group settings (basic)

Name

Values (Range)

Unit

Step

Default

Description

Operation

Off
On

–

–

Off

Operation Off / On

UMin>

5.0 – 100.0

%UB

0.1

75.0

Minimum bus voltage for operation
in
% of UBase

CompEnable

Disable
Enable

–

–

Enable

Selection of neutral voltage unbalance
compensation

UNUnbalWrn>

1.0 – 95.0

%UB

0.1

1.0

Neutral voltage unbalance warning level
in % of UBase

tDefWrn

0.00 – 60.00

s

0.01

5.00

Definite time delay to warning

UNUnbalAlm>

1.0 – 95.0

%UB

0.1

2.5

Neutral voltage unbalance alarm level
in % of UBase

tDefAlm

0.00 – 60.00

s

0.01

5.00

Definite time delay to alarm

UNUnbal>

1.0 – 95.0

%UB

0.1

5.5

Neutral voltage unbalance trip level
in
% of UBase

CurveType

Definite time
Programmable

–

–

Definite time

Selection of time delay curve type for
trip

tDefTrip

0.00 – 60.00

s

0.01

5.00

Definite time delay for trip

k

0.05 – 15.00

–

0.01

0.05

Time multiplier for programmable curve
for trip

tMin

0.00 – 60.00

s

0.01

0.10

Minimum operate time for programmable
curve for trip

tReset

0.00 – 60.00

s

0.01

0.02

Reset time delay for warning, alarm and
trip

tPCrv

0.000 – 3.000

–

0.001

1.000

Parameter P for programmable curve for
trip

tACrv

0.005 – 200.000

–

0.001

1.000

Parameter A for programmable curve for
trip

tBCrv

0.50 – 100.00

–

0.01

1.00

Parameter B for programmable curve for
trip

tCCrv

0.0 – 1.0

–

0.1

0.0

Parameter C for programmable curve for
trip

tDCrv

0.000 – 60.000

–

0.001

0.000

Parameter D for programmable curve for
trip

CrvSat

0 – 100

–

1

0

Tuning parameter for programmable curve

SCUVPTOV Non group settings (advanced)

SCUVPTOV Non group settings (advanced)

Name

Values (Range)

Unit

Step

Default

Description

BlockTrip

Trip disabled
Trip enabled

–

–

Trip enabled

Trip blocked /
enabled

SCUVPTOV Monitored data

SCUVPTOV Monitored data

Name

Type

Values (Range)

Unit

Description

LASTCOMP

GROUP SIGNAL

–

–

Indicates date and time when the last
trigger was made for compensation

UNUNBAL

REAL

–

kV

Instantaneous magnitude of capacitor
bank neutral unbalance voltage

PUNUNBAL

REAL

–

%

Capacitor bank neutral unbalance voltage
in % of UBase

UL1

REAL

–

kV

Bus voltage of phase L1

UL2

REAL

–

kV

Bus voltage of phase L2

UL3

REAL

–

kV

Bus voltage of phase L3

UNSCB

REAL

–

kV

Capacitor bank neutral voltage

K1USED

REAL

–

–

Used compensation factor of K1 for
unbalance neutral voltage calculation

K2USED

REAL

–

–

Used compensation factor of K2 for
unbalance neutral voltage calculation

K1MON

REAL

–

–

Monitored compensation factor of K1 for
unbalance neutral voltage calculation

K2MON

REAL

–

–

Monitored compensation factor of K2 for
unbalance neutral voltage calculation

Technical data

Logics & highlights

Protection scheme for ungrounded double WYE capacitor bank

Single line diagram for an ungrounded double WYE capacitor bank

Units arrangement in an ungrounded double WYE connected capacitor bank

Single line diagram for an ungrounded single WYE capacitor bank

Units arrangement in an ungrounded single WYE connected capacitor bank

Ungrounded single WYE SCB connected to function block

Any internal fault in the capacitor bank leads to unbalance in the shunt capacitor banks (SCB) and severe damage to the entire bank, which can result in an explosion or fire. In the shunt capacitor bank, the internal faults are due to open-circuit or short circuit of the capacitor units or elements. The “Phase voltage differential based capacitor bank unbalanced protection” can detect the voltage unbalance in the capacitor bank. It can be applied to grounded and ungrounded capacitor bank configurations, where the three-phase bus and tap voltage measurements are available.

For more detailed information on “Phase voltage differential based capacitor bank unbalanced protection” function, refer to ABB, Relion 670 Series manuals.

Phase voltage differential based capacitor bank unbalanced
protection

SCPDPTOV

Ud >

87V

Signals & Setting Parameters

SCPDPTOV function block

SCPDPTOV Input signals

SCPDPTOV Input signals

Name

Type

Default

Description

U3P

GROUP SIGNAL

–

Group signal for three phase bus
voltage

U3PTAP

GROUP SIGNAL

–

Group signal for three phase tap
voltage

U3NEUT

GROUP SIGNAL

–

Group signal for capacitor bank neutral
voltage

BLOCK

BOOLEAN

0

Block of function

BLKTR

BOOLEAN

0

Block of trip

BLKALM

BOOLEAN

0

Block of alarm

BLKWRN

BOOLEAN

0

Block of warning

INHIBIT

BOOLEAN

0

Inhibit the function

TRIGCOMP

BOOLEAN

0

Trigger input to store the voltage
ratios into the IED memory. The stored values will be used for future
compensation in the function.

RESETCOMP

BOOLEAN

0

Reset the stored voltage ratios to set
voltage ratio value

SCPDPTOV Output signals

SCPDPTOV Output signals

Name

Type

Description

TRIP

BOOLEAN

General trip signal

TRL1

BOOLEAN

Trip signal from phase L1

TRL2

BOOLEAN

Trip signal from phase L2

TRL3

BOOLEAN

Trip signal from phase L3

START

BOOLEAN

General start signal

STL1

BOOLEAN

Start signal from phase L1

STL2

BOOLEAN

Start signal from phase L2

STL3

BOOLEAN

Start signal from phase L3

ALARM

BOOLEAN

General alarm signal

ALML1

BOOLEAN

Alarm signal from phase L1

ALML2

BOOLEAN

Alarm signal from phase L2

ALML3

BOOLEAN

Alarm signal from phase L3

WARNING

BOOLEAN

General warning signal

WRNL1

BOOLEAN

Warning signal from phase L1

WRNL2

BOOLEAN

Warning signal from phase L2

WRNL3

BOOLEAN

Warning signal from phase L3

BLKDL1

BOOLEAN

Function operation blocked due to bus voltage in phase L1
or all three phase equivalent tap voltages going below UMin>

BLKDL2

BOOLEAN

Function operation blocked due to bus voltage in phase L2
or all three phase equivalent tap voltages going below UMin>

BLKDL3

BOOLEAN

Function operation blocked due to bus voltage in phase L3
or all three phase equivalent tap voltages going below UMin>

DIFURATL1

BOOLEAN

Alarm when deviation between the calculated and the set
voltage ratio for phase L1 is larger than the set threshold limit for
percentage variation (URatioVar>)

DIFURATL2

BOOLEAN

Alarm when deviation between the calculated and the set
voltage ratio for phase L2 is larger than the set threshold limit for
percentage variation (URatioVar>)

DIFURATL3

BOOLEAN

Alarm when deviation between the calculated and the set
voltage ratio for phase L3 is larger than the set threshold limit for
percentage variation (URatioVar>)

COMPEXED

BOOLEAN

Indicates that a trigger was made for compensation

PUDIFL1

REAL

Differential voltage magnitude of phase L1 in % of UBase

PUDIFL2

REAL

Differential voltage magnitude of phase L2 in % of UBase

PUDIFL3

REAL

Differential voltage magnitude of phase L3 in % of UBase

USEDURATL1

REAL

Magnitude of ratio between tap and bus voltages stored and
used for calculation of differential voltage of phase L1

USEDURATL2

REAL

Magnitude of ratio between tap and bus voltages stored and
used for calculation of differential voltage of phase L2

USEDURATL3

REAL

Magnitude of ratio between tap and bus voltages stored and
used for calculation of differential voltage of phase L3

URATIOL1

REAL

Magnitude of ratio between tap and bus voltages of phase
L1

URATIOL2

REAL

Magnitude of ratio between tap and bus voltages of phase
L2

URATIOL3

REAL

Magnitude of ratio between tap and bus voltages of phase
L3

SCPDPTOV Non group settings (basic)

SCPDPTOV Non group settings (basic)

Name

Values (Range)

Unit

Step

Default

Description

SCBGndType

Grounded
Ungrounded

–

–

Grounded

Selection of shunt capacitor bank
ground type

NeutVoltMeas

Not available
Available

–

–

Available

Selection of shunt capacitor bank
neutral voltage VT availability

GlobalBaseSel

1 – 12

–

1

1

Selection of one of the Global Base
Value groups

VoltRatioL1

0.010 – 0.950

–

0.001

0.500

Voltage ratio of tap voltage to bus
voltage for phase L1

VoltRatioL2

0.010 – 0.950

–

0.001

0.500

Voltage ratio of tap voltage to bus
voltage for phase L2

VoltRatioL3

0.010 – 0.950

–

0.001

0.500

Voltage ratio of tap voltage to bus
voltage for phase L3

SCPDPTOV Group settings (basic)

SCPDPTOV Group settings (basic)

Name

Values (Range)

Unit

Step

Default

Description

Operation

Off
On

–

–

Off

Operation Off / On

URatioVar>

5 – 300

%

1

10

Threshold limit for percentage
variation of calculated voltage ratio from set voltage ratios (VoltRatioLx,
where Lx is phase L1, L2 and L3)

UMin>

5.0 – 100.0

%UB

0.1

50.0

Minimum bus voltage for operation
in
% of UBase

UdifWrn>

1.0 – 95.0

%UB

0.1

5.0

Phase voltage differential warning
level in % of UBase

tDefWrn

0.00 – 60.00

s

0.01

5.00

Definite time delay to warning

UdifAlm>

1.0 – 95.0

%UB

0.1

8.0

Phase voltage differential alarm level
in % of UBase

tDefAlm

0.00 – 60.00

s

0.01

5.00

Definite time delay to alarm

Udif>

1.0 – 95.0

%UB

0.1

10.0

Phase voltage differential trip level
in
% of UBase

CurveType

Definite time
Programmable

–

–

Definite time

Selection of time delay curve type for
trip

tDefTrip

0.00 – 60.00

s

0.01

5.00

Definite time delay for trip

k

0.05 – 1.10

–

0.01

0.05

Time multiplier for programmable curve
for trip

tMin

0.00 – 60.00

s

0.01

0.10

Minimum operate time for programmable
curve for trip

tReset

0.00 – 60.00

s

0.01

0.02

Reset time delay for warning, alarm and
trip

tPCrv

0.000 – 3.000

–

0.001

1.000

Parameter P for programmble curve for
trip

tACrv

0.005 – 200.000

–

0.001

1.000

Parameter A for programmble curve for
trip

tBCrv

0.50 – 100.00

–

0.01

1.00

Parameter B for programmble curve for
trip

tCCrv

0.0 – 1.0

–

0.1

0.0

Parameter C for programmble curve for
trip

tDCrv

0.000 – 60.000

–

0.001

0.000

Parameter D for programmble curve for
trip

CrvSat

0 – 100

–

1

0

Tuning parameter for programmable curve

SCPDPTOV Non group settings (advanced)

SCPDPTOV Non group settings (advanced)

Name

Values (Range)

Unit

Step

Default

Description

BlockTrip

Trip disabled
Trip enabled

–

–

Trip enabled

Trip blocked /
enabled

SCPDPTOV Monitored data

SCPDPTOV Monitored data

Name

Type

Values (Range)

Unit

Description

LASTCOMP

GROUP SIGNAL

–

–

Indicates date and time when the last
trigger was made for compensation

UDIFL1

REAL

–

kV

Magnitude of differential voltage of
phase L1

UDIFL2

REAL

–

kV

Magnitude of differential voltage of
phase L2

UDIFL3

REAL

–

kV

Magnitude of differential voltage of
phase L3

PUDIFL1

REAL

–

%

Differential voltage magnitude of phase
L1 in % of UBase

PUDIFL2

REAL

–

%

Differential voltage magnitude of phase
L2 in % of UBase

PUDIFL3

REAL

–

%

Differential voltage magnitude of phase
L3 in % of UBase

UL1

REAL

–

kV

Bus voltage of phase L1

UL2

REAL

–

kV

Bus voltage of phase L2

UL3

REAL

–

kV

Bus voltage of phase L3

UTAPL1

REAL

–

kV

Tap voltage of phase L1

UTAPL2

REAL

–

kV

Tap voltage of phase L2

UTAPL3

REAL

–

kV

Tap voltage of phase L3

UNSCB

REAL

–

kV

Measured voltage at capacitor bank
neutral

USEDURATL1

REAL

–

–

Magnitude of ratio between tap and bus
voltage used for calculation of differential voltage of phase L1

USEDURATL2

REAL

–

–

Magnitude of ratio between tap and bus
voltage used for calculation of differential voltage of phase L2

USEDURATL3

REAL

–

–

Magnitude of ratio between tap and bus
voltage used for calculation of differential voltage of phase L3

URATIOL1

REAL

–

–

Magnitude of ratio between tap and bus
voltage of phase L1

URATIOL2

REAL

–

–

Magnitude of ratio between tap and bus
voltage of phase L2

URATIOL3

REAL

–

–

Magnitude of ratio between tap and bus
voltage of phase L3

Logics & highlights

Single line diagram of the typical single WYE shunt capacitor bank configuration

Differential voltage calculation

Voltage ratio calculation

Grounded single WYE connected SCB

Calculation for grounded capacitor bank

Ungrounded single WYE connected SCB

Calculation for ungrounded capacitor bank

Programmable curve

Simplified Warning, Alarm, and Trip logic

INHIBIT and BLOCK behavior in the function

Cyclic reporting of calculated and stored voltage ratios over IEC 61850

Any internal fault in the capacitor bank leads to unbalance in the Shunt capacitor banks (SCB) and severe damage to the entire bank, which can result in an explosion or fire. Generally internal faults in the shunt capacitor bank are due to the open or short-circuit of the capacitor units or elements. The “Current unbalance protection of SCB” function uses measured phase current (I3P) and measured unbalance current (I3UNB). Based on the measured unbalance current deviation from the stored reference current value, the function identifies the severity of the internal fault in the SCB.

For more detailed information on “Current unbalance protection of SCB” function, refer to ABB, Relion 670 Series manuals.

Trigger input to store the measured
quantities into the IED memory. The stored values will be used for future
compensation of the function measurement.

RESETCOMP

BOOLEAN

0

Force the stored natural unbalance
current and stored reference current to zero.

SCUCPTOC (60N) Output signals

SCUCPTOC (60N) Output signals

Name

Type

Description

TRIP

BOOLEAN

Common trip signal

TR_A

BOOLEAN

Trip signal from either phase A or from the neutral
unbalance depending how many unbalance currents are used (3 or 1).

TR_B

BOOLEAN

Trip signal from phase B. Forced to zero when only one
unbalance current is used.

TR_C

BOOLEAN

Trip signal from phase C. Forced to zero when only one
unbalance current is used.

BFI

BOOLEAN

Common pickup signal

PU_A

BOOLEAN

Start signal from either phase A or from the neutral
unbalance depending how many unbalance currents are used (3 or 1).

PU_B

BOOLEAN

Start signal from phase B. Forced to zero when only one
unbalance current is used.

PU_C

BOOLEAN

Start signal from phase C. Forced to zero when only one
unbalance current is used.

ALARM

BOOLEAN

General alarm signal

ALMA

BOOLEAN

Alarm signal for either phase A or for the neutral
unbalance depending how many unbalance currents are used (3 or 1)

ALMB

BOOLEAN

Alarm signal from phase B. Forced to zero when only one
unbalance current is used.

ALMC

BOOLEAN

Alarm signal from phase C. Forced to zero when only one
unbalance current is used.

WARNING

BOOLEAN

General warning signal

WRNA

BOOLEAN

Warning signal for either phase A or for the neutral
unbalance depending how many unbalance currents are used (3 or 1).

WRNB

BOOLEAN

Warning signal from phase B. Forced to zero when only one
unbalance current is used.

WRNC

BOOLEAN

Warning signal from phase C. Forced to zero when only one
unbalance current is used.

BLKDA

BOOLEAN

Phase A or neutral unbalance operation blocked, depending
how many unbalance currents are used (3 or 1), when corresponding reference
current going lower than set IMin value

BLKDB

BOOLEAN

Phase B operation blocked when corresponding reference
current goes lower than set IMin value. Forced to zero when only one
unbalance current is used.

BLKDC

BOOLEAN

Phase C operation blocked when corresponding reference
current goes lower than set IMin value. Forced to zero when only one
unbalance current is used.

COMPEXED

BOOLEAN

Indicates that a trigger was made for natural unbalance
current calculation

IUNBCLCA

REAL

Magnitude of calculated unbalance current for either phase
A or neutral unbalance depending how many unbalance currents are used (3 or
1).

IUNBCLCB

REAL

Magnitude of calculated unbalance current of phase B.
Forced to zero when only one unbalance current is used.

IUNBCLCC

REAL

Magnitude of calculated unbalance current of phase C.
Forced to zero when only one unbalance current is used.

SCUCPTOC Non group settings (basic)

SCUCPTOC Non group settings (basic)

Name

Values (Range)

Unit

Step

Default

Description

SCBConf

1 unbalance curr
3 unbalance curr

–

–

1 unbalance curr

Number of unbalance currents available

GlobalBaseSel1

1 – 12

–

1

1

Global base value selector for phase
current

GlobalBaseSel2

1 – 12

–

1

1

Global base value selector for
unbalance current

SCUCPTOC Group settings (basic)

SCUCPTOC Group settings (basic)

Name

Values (Range)

Unit

Step

Default

Description

Operation

Off
On

–

–

Off

Operation Off / On

IMin

5.0 – 100.0

%IB1

0.1

10.0

Minimum reference phase current for
operation in % of IBase1 with reference to phase current CT

IUnbalWrn>

1.0 – 1000.0

%IB2

0.1

10.0

Current unbalance warning level for
unbalance current in % of IBase2 with reference to unbalance current CT

tDefWrn

0.00 – 60.00

s

0.01

5.00

Definite time delay for warning

IUnbalAlm>

1.0 – 1000.0

%IB2

0.1

20.0

Current unbalance alarm level for
unbalance current in % of IBase2 with reference to unbalance current CT

tDefAlm

0.00 – 60.00

s

0.01

5.00

Definite time delay for alarm

IUnbal>

1.0 – 1000.0

%IB2

0.1

30.0

Current unbalance trip level for
unbalance current in % of IBase2 with reference to unbalance current CT

CurveType

Definite time
Programmable

–

–

Definite time

Selection of time delay curve type for
trip

tDefTrip

0.00 – 60.00

s

0.01

5.00

Definite time delay for trip. Note that
when Programmable IDMT curve is used, this definite time delay will be added
to the calculated IDMT time.

k

0.05 – 999.00

–

0.01

1.00

Time multiplier for programmable curve
for trip

tMin

0.00 – 60.00

s

0.01

0.00

Minimum operate time for programmable
curve for trip

tReset

0.00 – 60.00

s

0.01

0.02

Reset time delay for warning, alarm and
trip

tPCrv

0.005 – 3.000

–

0.001

2.00

Parameter P for programmble curve for
trip

tACrv

0.005 – 200.000

–

0.001

28.200

Parameter A for programmble curve for
trip

tBCrv

0.0000 – 20.0000

–

0.0001

0.1217

Parameter B for programmble curve for
trip

tCCrv

0.1 – 10.0

–

0.1

1.0

Parameter C for programmble curve for
trip

SCUCPTOC Non group settings (advanced)

SCUCPTOC Non group settings (advanced)

Name

Values (Range)

Unit

Step

Default

Description

BlockTrip

Trip disabled
Trip enabled

–

–

Trip enabled

Trip blocked /
enabled

SCUCPTOC Monitored data

SCUCPTOC Monitored data

Name

Type

Values (Range)

Unit

Description

LASTCOMP

GROUP SIGNAL

–

–

Indicates date and time when last trigger was made for natural
unbalance current calculation

IUNBCLCL1

REAL

–

A

Magnitude of calculated unbalance current for either phase L1 or
neutral unbalance depending how many unbalance currents are used (3 or 1).

IUNBCLCL2

REAL

–

A

Magnitude of calculated unbalance current of phase L2. Forced to
zero when only one unbalance current is used.

IUNBCLCL3

REAL

–

A

Magnitude of calculated unbalance current of phase L3. Forced to
zero when only one unbalance current is used.

IL1

REAL

–

A

Reference quantity which is either phase L1 current or positive
sequence current depending how many unbalance currents are used (3 or 1).

IL2

REAL

–

A

Current in phase L2. Forced to zero when only one unbalance
current is used.

IL3

REAL

–

A

Current in phase L3. Forced to zero when only one unbalance
current is used.

IUNBL1

REAL

–

A

Unbalance current in either phase L1 or neutral depending how
many unbalance currents are used (3 or 1).

IUNBL2

REAL

–

A

Unbalance current in phase L2. Forced to zero when only one
unbalance current is used.

IUNBL3

REAL

–

A

Unbalance current in phase L3. Forced to zero when only one
unbalance current is used.

IMEML1

REAL

–

A

Stored value for either phase L1 current or positive sequence
current depending how many unbalance currents are used (3 or 1).

IMEML2

REAL

–

A

Stored phase current of phase L2. Forced to zero when only one
unbalance current is used.

IMEML3

REAL

–

A

Stored phase current of phase L3. Forced to zero when only one
unbalance current is used.

IMEMUNBL1

REAL

–

A

Stored unbalance current for either phase L1 or neutral
depending how many unbalance currents are used (3 or 1).

IMEMUNBL2

REAL

–

A

Stored unbalance current of phase L2. Forced to zero when only
one unbalance current is used.

IMEMUNBL3

REAL

–

A

Stored unbalance current of phase L3.
Forced to zero when only one unbalance current is used.

IREFUNBL1

REAL

–

A

Magnitude of stored unbalance current
scaled to the reference quantity for either phase L1 or neutral depending how
many unbalance currents are used (3 or 1).

IREFUNBL2

REAL

–

A

Magnitude of stored unbalance current
scaled to present phase current of phase L2. Forced to zero when only one
unbalance current is used.

IREFUNBL3

REAL

–

A

Magnitude of stored unbalance current
scaled to present phase current of phase L3. Forced to zero when only one
unbalance current is used.

Cascading failures are series faults in shunt capacitor banks involving more than one capacitor unit (or even more than one rack). They are characterized by the presence of an unbalanced shunt capacitor bank (SCB) current. However, as the connected power system is much stronger than the SCB rating, any unbalance voltage due to cascading faults inside the capacitor bank is typically not present in the system. The “Shunt capacitor cascading failure protection” function provides protection against cascading faults and has two modes to detect the unbalances.

For more detailed information on “Shunt capacitor cascading failure protection” function, refer to ABB, Relion 670 Series manuals.