2. Under/Over Voltage Protection
Under/over Voltage Protection can be configured to cause the
recloser to trip, if the measured system voltage goes outside
preset limits for a preset time.
The recloser uses logic based on ‘AND’, ‘OR’ or ‘AVERAGE’
evaluation to determine if the system voltage maintains a
‘normal voltage’ state.
A recloser can be configured to automatically reclose after an
under or over voltage protection trip, if the system voltage has
returned to an acceptable value.
3. Voltage Protection can also be configured to:
Force ‘voltage protection’ off in the case of excessive voltage
protection sequences.
Force ‘normal voltage close’ off in the case of a voltage
protection recovery timeout.
8. Over Voltage Protection Timing
V
O
L
T
A
G
E
tSwitchgear Status
6300V
7560V
6930V
Over Voltage Pickup
Over Voltage Reset 7434V
Over Voltage Normal
Over Voltage Normal Reset
7056V
CLOSEDOPENCLOSED
Over Voltage
Pickup at this time
Over Voltage
Reset at this time
Over Voltage
Trip Delay Timer
Trip at this time
Normal Voltage
Close Time
Close at this time
10. Under and Over Voltage Phase Logic Options
Phase Logic controls the method in which measured voltages are
evaluated against the under/over Voltage Threshold.
The Options are:
AND
All measured phase voltages must deviate beyond the
Pickup Threshold for pickup to occur.
OR
Any measured phase voltage which deviates beyond the
Pickup Threshold will cause pickup to occur.
AVERAGE
The numerical average of all three measured phase
voltages must deviate beyond the Pickup Threshold for
pickup to occur.
13. Normal Voltage Close ON/OFF
Normal Voltage Close ON enables the controllers normal
voltage close functionality which causes the ACR to
automatically close when:
The most recent trip was a UOV protection trip,
The switchgear source side voltages have returned to a
‘Normal Voltage’ state,
‘Normal Voltage Close’ was ON before the UOV trip and is still
ON,
AND
The ‘Normal Voltage’ state has persisted for the duration of
the Normal Voltage Close Delay time period.
15. Voltage Protection Recovery Timeout Operation
If Normal Voltage Close is ON
and the switchgear does not
‘Normal Voltage Close’
subsequent to a
‘UOV Protection Trip’
in less than or equal to the
‘Normal Recovery’ period
then:
‘Normal Voltage Close’ will be forced OFF
And
The Switchgear will go to ‘Lockout’
Range 0 – 1000s
Setting Recovery Time Out to
Off
Will inhibit this feature
17. Excess UOV Protection Sequences
If the number of Voltage Protection sequences equals the
‘excess sequence’ count threshold
within the voltage sequence count accumulation period then:
Under Voltage Trip
Over Voltage Trip
Normal Voltage Close …….. Will all be forced OFF
18. Single Sided CVT Switchgear
If UOV Protection is Available on the controller
and the attached switchgear is only fitted with CVT’s on one side
and if the controllers Source/Load designation is set such that the
designated Load side has the CVT’s fitted
Then UOV Protection ‘Normal Voltage Close’ will be forced to OFF
and if the switchgear is in a UOV Protection tripped state,
Then the switchgear will go to Lockout.
19. Protection Menu Navigation
6x Earth Protection Settings
6x NPS Protection Settings
3x Global Protection Settings
2x Protection Features Settings
2x Frequency Protection Settings
6x Phase Protection Settings
3x Under/Over Voltage Settings
21. Questions?
On which screen can Under/Over Voltage Protection be made available
via the OCPM?
Options 3 in the System Status menu.
With UOV Phase Logic set to ‘Average’, what voltage value will the
protection use for A = 0V B = 15000V C = 16000V?
15500V
At which voltage will the Normal Voltage Close timer start following an
Over Voltage trip with the following settings?
Over Voltage trip at: 15000V
Over Voltage normal at: 14000V
Nominal Phase to Earth 12600V
14000V
How many UOV Protection screens are on the OCPM and where?
Three screens at the end of the Protection menu.
Editor's Notes
Under/Over voltage protection takes periodic voltage measurements, compares them to thresholds derived from the nominal system voltage and in conjunction with certain voltage protection configurations, determines if the measured voltage(s) maintain a ‘normal voltage’ state.
Before UOV Protection can be put into service the ‘Nominal System (RMS Phase/Earth) Voltage’ (the system voltage) MUST be known.
UOV Protection is not active unless a phase on the designated source side of the switchgear is ‘LIVE’ with respect to the ‘Live/Dead’ indication.
Should the switchgear’s designated source side voltages ALL fall below the ‘Live/Dead’ threshold then any UOV protection sequence is ‘Reset’.
The Under/Over Voltage capability has been included in CAPM code x28-13.00+
Before configuring a new off-line file in WSOS, Under/Over Voltage Protection must be added to the Selected Capability list.
Under/Over Voltage protection can be configured in WSOS by clicking on the Voltage Protection button on the protection page.
This button will be greyed out unless Voltage Protection has been made available.
In WSOS, Voltage Protection can be made available on the Protection Control page and on the OCPM on the Options 3 screen.
Under and Over Voltage protection can be configured individually.
This means that one or the other or both can be on.
Each element has Trip, Normal and Time to Trip settings as well as logic options.
The Over Voltage threshold is expressed as a percentage of the nominal system voltage.
.
The four voltage settings, Over Voltage Trip, Over Voltage Normal, Under Voltage Trip and Under Voltage Normal have deadbands associated with them.
These deadbands are always 2% of the Nominal System Voltage (as configured).
If the measured voltage and Phase Logic evaluation results in an ‘Over Voltage Pickup’ and the ‘pickup’ state persists continuously for a period greater than the Over Voltage Trip Delay Timer, and Over Voltage Trip is ON, then the Over Voltage trip request is issued and logged.
The above also applies to Under Voltage protection.
The voltage derived for the protection does not take into account any phase value that is below the Live/Dead threshold level.
If any of the following settings change during an UOV protection sequence, the sequence will be aborted and if the switchgear was tripped by voltage protection, then the switchgear state will also go to Lockout.
Normal Voltage Close
Normal Voltage Close time delay
Voltage thresholds (normal or pickup)
Phase Logic
Under/Over Voltage Trip ON/OFF
Under/Over Voltage Trip Delay
Excess Sequence time
Excess sequence Threshold
Recovery Time
Load/Source designation
Protection OFF
Active Protection Group
When a Normal Voltage Close occurs, an event will be logged in the Event Log.
When Normal Voltage Close is ON and a UOV protection trip occurs, no lockout event is generated and the OCPM display does not show ‘Lockout’,
If Normal Voltage Close is turned OFF subsequent to a UOV protection trip but before the switchgear has ‘Normal Voltage’ closed, then a lockout event will be generated and the OCPM ‘Operator Settings’ page will display ‘Lockout’ and the ‘Alert title lines will be removed.
The under and over normal voltage threshold’s are expressed as percentages of the system voltage and denote the Normal Voltage range’s upper and lower bounds (dead bands withstanding).
When the evaluated voltages and phase logic result is within these bounds (plus dead bands) UOV protection is in the ‘Normal Voltage’ state.
The Normal Voltage Close Delay timer starts timing subsequent to a UOV protection trip when the measured voltages have returned to a ‘Normal Voltage’ state and Normal Voltage Close is ON.
The timer is reset whenever the evaluated voltages deviate from the ‘Normal Voltage’ state.
A UOV protection close request is generated when the timer reaches the configured normal voltage close delay time.
