2. Overview
The purpose of this presentation is to
explain the operation of the various
protection features used with the PTCC.
The following topics will be covered:
Sequence Control
Live Load Blocking
Dead Lockout
High Current Lockout
Inrush Restraint
Cold Load Pickup
Single Shot
Work Tag
3. Objectives
At the end of this training session, you should be able to:
Understand how protection and reclosing operations can
be modified by the use of the various protection features
that are available on the PTCC.
4. Sequence Control
Where more than one recloser is installed on a feeder, the
upstream device must always be coordinated with the
downstream device for faults seen by both.
They can become uncoordinated if the fault is still present when
the downstream device trips and recloses.
In this case the downstream device will begin timing to trip
according to its Trip 2 settings and if the upstream device has
also detected the fault it will calculate the time to trip according
to its Trip 1 settings.
For a given fault, the upstream device’s Trip 1 time might be
shorter than the downstream device’s Trip 2 time.
This could cause an unnecessary loss of supply to the load
connected between the two devices.
5. Sequence Control OFF
PickupPickupPickup
Active Settings = Trip 1 Active Settings = Trip 1Active Settings = Trip 2
Auto ReclosePickup
Auto Reclose ON Auto Reclose ON
F - S - S - F F - S - S - FF - S - S - F
6. Sequence Control ON
PickupPickupPickup
Active Settings = Trip 1 Active Settings = Trip 1Active Settings = Trip 2
Auto ReclosePickup
Active Settings = Trip 2
Auto Reclose ON Auto Reclose ON
F - S - S - F F - S - S - FF - S - S - FF - S - S - F
15. System Status Menu Navigation
1x Trip Flags
2x Operator and System Settings
8x Switchgear Status and Settings
3x Options
1x Quick Key Selection
1x WSOS Port P8 Communications
1x IOEX Status
13x Communications Setup
17. Dead Lockout
When Dead Lockout is ON, the recloser
will not automatically reclose unless one
or more of the source side or load side
terminals are live.
If all the terminals are dead following a
protection trip, the controller will go to
lockout.
Dead Lockout
20. Dead Lockout Summary
Dead Lockout only applies when Auto Reclose is ON.
The controller checks for Source side voltages and load side
voltages if they are available immediately prior to the
scheduled Auto Reclose event.
Unless at least one of the source or load bushings is live,
Auto Reclose is aborted and the recloser goes to lockout.
Dead Lockout cannot be turned ON if the source side
voltages are unavailable.
Therefore, a U Series recloser without voltage sensing on
the x side cannot use Dead Lockout if the x side is the
designated source.
21. Dead Lockout Events
When Dead Lockout occurs, a Dead
Lockout event is logged as well as the
usual Lockout event.
23. High Current Lockout
This feature can be used to prevent the
recloser from closing onto a large or
persistent fault.
24. High Current Lockout Settings
High Current Lockout operates according
to two settings:
Lockout Current
Active Trip No.
25. High Current Lockout Operation
Auto Reclose ON
High Current Lockout ON
• Lockout current = 500A
• Active Trip = Trip 1
300 A550 A
High Current Lockout
26. High Current Lockout Summary
Normal Protection Trip occurs with High
Current Lockout and Auto Reclose ON.
The controller checks if:
The max current measurement for
the most recent protection trip,
exceeds the HCL current setting.
The trip number of the most recent
protection trip is equal to or greater
than the HCL active trip number.
If both of the above conditions are true,
the recloser records that the high current
setting was exceeded and goes to
lockout.
27. 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
30. High Current Lockout and Single Shot
High Current Lockout can occur when
Single Shot Mode is active or when
closing onto a fault by an operator.
In both of these situations the controller
would have gone to lockout anyway
without High Current Lockout being
triggered.
The difference is that, if High Current
Lockout was triggered, an event will be
recorded in the Event Log as extra
information for fault analysis.
31. Inrush Restraint
Inrush Restraint works by raising the
phase and earth Threshold Currents for a
short period of time to allow the inrush
current to subside.
Inrush Restraint is armed for operation
whenever the load current goes to zero.
When the load at a later time becomes
non-zero the Inrush Restraint is
activated and the Inrush Multiplier is
used in place of the Threshold Current
Multiplier for the set time.
33. Inrush Restraint Operation
Time (s)
0.00
C
u
r
r
e
n
t
100 A
200 A
300 A
0.10 0.20 0.30 0.40 0.50 0.60 0.70
Trip Setting
Measured Current
At this point, current goes
from zero to non-zero.
IR Time = 200ms IR Multiplier = 2
34. Inrush Restraint Effect on Protection Curve
220A 400A220A
0.00 Current zero
Time(s) Event
1.00 Current non zero
1.10 IR timer expired
Inrush
Restraint
Settings:
IR Time
IR Multiplier
Protection
Settings:
Phase Trip = 200A
Threshold
Multiplier = 1.1
100ms
X 2
35. Inrush Restraint – Points to Remember
Inrush Restraint affects phase and earth
protection, but does not apply to Definite
Time or SEF.
If normal currents are expected to drop
below 2.5A, then Inrush cannot be used.
In this case Inrush Restraint should be
turned off.
40. Cold Load Pickup
When a typical load has been without
supply for a period of time (hours) it loses
its diversity.
When power is restored the load is
higher than usual because all the heater,
refrigeration or air conditioner
thermostats have turned on.
The longer the period without supply the
greater the loss of diversity and the
higher the load current will be when
supply is restored.
41. Cold Load Pickup vs Inrush Restraint
Time
Inrush Restraint normally operates over 100 – 200ms.
Cold Load operates over a number of hours.
Multiple
Inrush Restraint applies a set multiple for a set time.
Cold Load applies a multiple which changes over time.
42. 1 + Operational Cold Load Time x (User Set Cold Load Multiplier –1)
User Set Cold Load Time
Operational Cold Load Multiplier =
Operational Cold Load Time
Time (min)
C
u
r
r
e
n
t
100 A
200 A
300 A
30 60 90 120 150 180 210
Trip Setting 100A
Load Current 50A
43. Operational Cold Load Status
Time
(min)
C
u
r
r
e
n
t
100 A
200 A
300 A
60 120 180 240 300 360 420
1 2 3
390
4
44. Load Off
Cold Load Pickup Effect on Protection Curve
220A240A260A280A300A320A340A360A380A400A220A
Protection Settings:
Phase Trip = 200A Threshold
Multiplier = 1.1
Load On
Elapsed Time
10 min20 min30 min40 min50 min60 min70 min80 min90 min
Cold Load
Pickup Settings:
CLP Time
CLP Multiplier
90 min
x 2
46. Cold Load Pickup – Points to Remember
The user-set Cold Load Time and Cold Load Multiplier are set
on the Protection Settings 5 screen.
On power up, the load is assumed to be diverse, i.e. the
Operational Cold Load Time is zeroed and ‘Cold Load IDLE’
will be displayed.
Cold Load affects phase and earth protection thresholds
including instantaneous but not SEF.
High Current Lockout and Definite Time settings are not
affected.
Cold Load Pickup cannot be used if normal currents are
expected to drop below 2.5A, and should be turned off.
When Cold Load protection is turned on the multiplier used for
Inrush will always be the higher of the Inrush Multiplier and the
Cold Load Multiplier.
48. Single Shot Mode
Single Shot Mode is used to provide an
appropriate protection curve when non-
reclosing operation is required, for
example, when closing onto a fault.
49. Single Shot Operation
In Single Shot Mode the controller goes directly to lockout after
one trip and will not Auto-Reclose.
Single Shot Mode is activated when:
Auto-Reclose is turned off and Work Tag is not applied.
The circuit breaker is closed by operator command
irrespective of the state of Auto-Reclose.
Single Shot is de-activated when:
Auto-Reclose is turned back on.
Work Tag is not active, and the Single Shot Timer expires
without a protection pickup ocurring.
50. Single Shot Timer
This timer starts when the switchgear
closes and runs for the preset number of
seconds.
This may be disabled by setting the
Single Shot reset time to zero.
When set to zero, auto-reclosing will
always be enabled while Auto Reclose is
ON.
52. Single Shot Timer initiated by Operator Close
Operator
Close
SS Timer
CB Status
t
Single Shot
Timer Expires
OPEN CLOSED
Single Shot
Timer Setting
Single Shot Mode
53. Protection Pickup during Single Shot Timing
CB Status
Pickup
t
SS Timer
Operator
Close
OPEN OPEN
Protection
Pickup
Single
Shot
Protection
Trip
CLOSED
Time to Trip
Single Shot
Timer Setting
Single Shot Mode
54. Protection Reset during Single Shot Timing
CB Status
Pickup
t
SS Timer
Operator
Close
OPEN
Protection
Pickup
CLOSED
Single Shot
Timer Setting
Protection
Reset
Single Shot Mode
Single Shot
Timer Expires
59. Work Tag
Applying the Work Tag ensures that
closing cannot take place at all, either by
a local operator, a remote operator or
automatically.
60. Protection Operation with Work Tag Applied
The switchgear cannot close while the
Work Tag is applied but Work Tag can be
applied when the switchgear is closed.
If a protection trip occurs while the Work
Tag is applied, the switchgear will always
go to lockout even if Auto Reclose is ON.
The protection pickup and time to trip will
be determined by the Work Tag
protection settings and Work Tag Trip will
be recorded in the Event Log.
65. Work Tags and Controller Mode
The controller is always in either Local or
Remote mode.
Only a local operator can apply/remove the
Work Tag when the controller is in Local Mode
and only a remote operator can apply/remove
the Work Tag when the controller is in Remote
Mode.
This means that a local operator can remove the
Work Tag applied by a remote operator but they
must first put the controller into Local mode.
66. Questions
In which Operator Panel menu is Sequence Control turned ON?
The Protection menu.
Can system voltage on the 1 (i) side prevent a recloser with Live Load Blocking ON from
being closed?
Yes, if the Power Direction setting is Source 2 – Load 1
(Source x – Load i).
What could prevent Dead Lockout from being turned on for a U Series ACR?
No x side voltage sensing and Power Direction set to Source x – Load i.
An ACR set for 4 trips to lockout recorded Trip 1 max I 1000A, Trip 2 max I 950A, Trip 3
max I 1040A, Trip 4 max I 1050A, Lockout. When would HCL have caused lockout if the
settings were: HCL Current 1000A, Trip No 2?
Lockout would have occurred after Trip 3.
To which of the following does Inrush Restaint not apply? SEF, Phase Faults, Definite
Time, Earth Faults.
SEF and Definite Time.
If the Cold Load status is: 60 min Mult x2 and the user set Cold Load Time is 120 min,
what must the user set Cold Load Multiplier be?
3.
How can the switchgear be closed when the Work Tag is applied?
It can’t.
Editor's Notes
Sequence control causes the recloser to step to the next count in the reclose sequence on reset of all protection elements whether or not the recloser tripped.
The sequence will only advance if Auto Reclose in on and the Single Shot Timer has timed out.
Consider a situation where there are two reclosers on a feeder.
Both are programmed for fast tripping on the first trip and slow tripping on the second trip in order to coordinate with fuses on the spur lines.
Suppose there is a fault downstream of the second recloser which is big enough to cause a protection pickup by the first recloser as well.
The recloser closest to the fault will trip and step onto the second set of protection settings which is a slow trip and then recloses.
If the fault has not been cleared the recloser nearest to the source is still on its fast trip settings and will now trip.
This situation would result in unnecessary loss of supply to the load connected to the first recloser.
The problem is overcome by setting Sequence Control On in the recloser nearest to the source.
When Sequence Control is On, the recloser steps onto the next stage in the protection trip sequence after it has seen a fault whether it tripped or not.
In this way an upstream recloser will keep its sequence coordinated with a downstream recloser.
If the fault is cleared the trip count will reset back to zero after the sequence reset timer in the normal way.
The SEF counter is also coordinated with the downstream recloser and will increment if its element has picked up.
In order to implement Live Load Blocking, it must be clearly understood what is meant by the terms: Load Side and Live.
Even though these settings are on the Measurement page in WSOS, they are not found in the Measurement menu on the operator panel
The ‘Live if’, ‘Supply Timeout’ and Power Flow settings are found on the ‘Phase Voltage and Power Flow’ screen in the System Status menu
When this feature was first implemented for the PTCC, only the Source side was checked for live bushings.
It was later changed to check all bushings to allow for situations where a source of supply may be connected to the load side.
Dead Lockout can be selected On or Off on the Control page of WSOS5.
Dead Lockout On/Off is an operator setting.
Dead Lockout On/Off is on the Operator Settings 2 screen in the System Status menu of the Operator Control Panel.
Dead Lockout is an operator setting and does not require the operator to enter a password.
Dead Lockout does not need load side voltages in order to operate, but it will use them if they are available.
Source side voltages must be available.
If Dead Lockout is On for a U Series recloser without x side voltage sensing and the power flow setting is changed from Source I – Load x to Source x – Load I, Dead Lockout will go from ON to OFF.
If this is done through WSOS, a message will appear to warn the operator that Dead Lockout has turned off.
A Dead Lockout event in the Event Log indicates that the recloser would have performed an automatic reclose if any of the HV bushings had been live at the time this was due to happen.
If a trip occurs and the measured maximum fault current exceeds the ‘High Current Lockout’ setting, the controller goes directly to lockout and will not reclose.
A High Current Lockout will only occur when the setting is equal to, or higher than the Phase trip setting.
The recloser can be forced to lockout where that is prefered to the possibility of closing onto a fault that exceeds the Lockout Current setting.
The Active Trip No allows the lockout to be delayed until a particular tirp is reached in the reclose sequence.
High Current Lockout does no effect the actual tripping of the recloser.
With High Current On, tripping will still occur according to the protection settings for the scheduled trip.
Immediately after the trip event, the controller checks the most recent trip to see if:
The max current recorded was greater than the HCL setting.
The trip count was equal to or greater than the HCL active trip number.
If both of the above conditions were met, the recloser goes to High Current Lockout.
When closing onto a typical load there is always a short lived inrush current caused by, for example, transformer magnetisation currents, low resistance lamp filaments and motors starting.
The purpose of Inrush Restraint is to prevent the circuit breaker from tripping when inrush currents occur.
Inrush Restraint affects Phase, Earth and NPS protection, but does not apply to Definite Time or SEF.
In this example, the IR multiple was applied to the trip setting for a duration of 200ms from when the current went from zero to non zero.
This could have been caused by the switchgear closing and taking load or the switchgear could have been already closed and the load could have been caused by another device either upstream or downstream closing.
The IR multiplier of 2 caused the trip setting to go from 100A to 200A for the duration of the IR time setting.
If the switchgear closes onto a fault but the fault current does not exceed the trip setting x the IR multiplier, the trip time to clear the fault will be extended by the IR time setting.
This slide shows the effect of Inrush Restraint on the actual protection curve.
While the current through the device is zero, the pickup current is 220A. This is due to a trip setting of 200A and a threshold multiplier of 1.1.
When the current goes from zero to non zero, the curve changes such that the pickup current is 400A. This is due to the Inrush Restraint multiple of 2 being applied to the trip setting of 200A.
Once the Inrush Restraint timer expires, the curve reverts to its original shape.
Inrush Restraint operates according to zero and non-zero current levels.
Currents below 2.5A can be interpreted as zero current and this could lead to Inrush Restraint being applied at the wrong time.
The Inrush Restraint settings can be view in WSOS5 by opening the Protection page and clicking Inrush Restraint on the left hand panel for the protection group required.
The Inrush Restraint settings can be found on the operator panel in the Protection menu.
These settings are in the second group of settings described as Protection Features Settings in the above slide.
The Inrush Restraint settings are on the fifth screen of the Protection Menu along with the Cold Load settings.
Cold Load is similar to Inrush Restraint in that they both have a Time and a Multiple setting.
The ranges for these settings are different.
For Inrush Restraint, the Time setting has a range of 0.05s to 30.0s. For Cold Load the range is 1 min to 480 min.
Inrush Restraint has a multiple setting range of 1 to 30 whereas the Cold Load multiple range is 1 to 5.
The Cold Load multiple varies with time. The value of the Cold Load multiple at a particular time can be calculated using the formulae in this slide.
The formulae contains two constant values which are the in service Cold Load settings and one variable which is the Operational Cold Load Time.
This is the time the load has been off (up to the Cold Load time setting), or the time the load has been off minus the time it has been back on.
In this example, the load goes off for one hour in which time the Operational Cold Load Multiplier goes from 1.0 to 3.0.
Over the next half hour the load remains off and the Operational Cold Load Multiplier stays at 3.0.
The load then come on and there is a heavy surge of current which gradually tapers off.
Over the next hour, the Operational Cold Load Multiplier ramps down from 3.0 to 1.0.
The CLP settings in this case would be: CLP Time 60 min
CLP Multiplier x3
The top left hand field on the Operator Settings 2 screen in the System Status menu displays the current status for the Cold Load Pickup.
Cold Load Pickup cannot be switched ON or OFF from this field. That must be done in the Protection Menu.
CLP OFF means that the feature is OFF and will have no effect on the protection settings.
CLP IDLE means that Cold Load Pickup is ON but not currently effecting the protection settings. As in 1.
At 2, the load has been off for one hour and the Operational Cold Load Multiple has ramped up from 1 to 2.
At 3, the Operational Cold Load Multiplier is at 3.0. This is equal to the Use Set Cold Load Multiplier which is the max value that can be attained. This value was reached after the load had been off for two hours.
At 4, the load has been back on for 90 min and the Operational Cold Load Multiplier has ramped down from 3 to 1.5.
The Cold Load Pickup settings for this example are:
CLP Time: 120 min CLP Multiplier: x3.
This slide shows the effect of Cold Load Pickup on the actual protection curve.
The protection settings as shown mean that pickup will normally occur at 220A.
When the load goes off with Cold Load on, the curve changes to adjust the pickup current until it reaches it’s maximum value after the Cold Load user set time.
Later when the load comes back on again, the pickup value will return to its original value over the Cold Load time setting duration.
To configure the Cold Load Pickup feature in WSOS5, select Cold Load on the left hand side of the main protection page.
The Cold Load Settings are:
Cold Load Time
Cold Load Multiplier
Cold Load ON/OFF
When the Single Shot Reset timer is set to zero, Single Shot Mode does not activate after an operator or automation close command.
If the Single Shot Mode is active when the switchgear is closed, ‘Single Shot Active’ is displayed in the bottom left hand field on the Operator Settings 1 screen in the System Status menu.
This field will go blank when the Single Shot timer expires.
The recloser is in Single Shot mode whenever Auto Reclose is OFF.
The recloser is also in Single Shot mode for a for a short period following an operator close. The duration of this period is determined by the Single Shot timer setting.
The Single Shot timer starts to run when an operator close occurs. If no fault is detected, the timer times out and the switchgear stays closed.
In this example, a protection pickup occurs during the Single Shot running time which resets the Single Shot timer.
The fault persists and a single shot trip occurs after the time to trip expires.
The time to trip may be longer than the the Single Shot Reset Time.
In other words it doesn’t matter how long the time to trip is, as long as pickup occurred while the single shot timer was running, it will result in a single shot trip.
If the protection resets following a pickup which occurred while the single shot timer was running, the single shot timer will restart.
The recloser will continue to be in single shot mode until the timer expires.
Clicking on the Single Shot button on the main Protection page launches the Single Shot Settings page.
This page includes the Single Shot Reset Time setting.
The page contains Earth, NPS and Phase Single Shot protection trip settings and is similar to the pages for Trips 1 – 4.
When Single Shot Mode is active the values set on the relevant Earth/Phase/NPS protection page are used.
When Single Shot Mode de-activates, protection reverts to the fully programmed sequence.
The Inrush Restraint settings can be found on the operator panel in the Protection menu.
These settings are in the second group of settings described as Protection Features Settings in the above slide.
Once the Work Tag is applied, neither a local user, remote user of the Auto-Reclose function can close the recloser.
Work Tag mode is activated when Work Tag is applied irrespective of Auto Reclose mode status, and is deactivated when the Work Tag is removed.
It is not possible for the operator to close the circuit breaker whilst in Work Tag mode.
If the Work Tag is deactivated whilst Auto Reclose is ON then the Auto Reclose mode will be entered immediately.
The Single Shot timer does not apply to Work Tag mode.
Once the Work Tag is applied, neither a local user, remote user of the Auto-Reclose function can close the recloser.
Work Tag mode is activated when Work Tag is applied irrespective of Auto Reclose mode status, and is deactivated when the Work Tag is removed.
It is not possible for the operator to close the circuit breaker whilst in Work Tag mode.
If the Work Tag is deactivated whilst Auto Reclose is ON then the Auto Reclose mode will be entered immediately.
The Single Shot timer does not apply to Work Tag mode.
To put the recloser into the Work Tag mode from WSOS, open the Control and Monitoring page and click on the Work Tag On/Off button.
Work Tag can be turned on in the normal way using the Select and arrow keys.
When the Work Tag has been applied, a warning message ‘Warning – Work Tag Applied’ flashes in the title field.
This message is always visible regardless of which screen is displayed.
Work Tag protection settings are used to provide an appropriate protection curve when the Work Tag has been applied.
There are separate pages for Phase Work Tag Protection, Earth Work Tag Protection and NPS Work Tag Protection.
Each page is similar to the normal protection trip pages.
There are three screens on the Operator Panel for the Work Tag protection settings.
The three screens are for Phase, Earth and NPS Work Tag Protection Trip settings.
They are in the Protection menu.
An important feature of the controller is that it is always in one of two modes, either Local or Remote, and can have a Work Tag applied by Local or Remote operators.
The mode and the tag specify the circumstances under which the switchgear can be closed to ensure operational safety.
