Classic LA Parameters

Overview

LA incorporates a number of parameters that must be correctly configured which helps to ensure the correct operation. These parameters may be set using WSOS or the O.I. except where noted.

Description of Parameters

Some of the following parameters are LA specific. Others are parameters that impact on LA and some are referenced in the LA Settings Record in Appendix L.3 Network Configuration Example.

Table 91 Description of Parameters – Classic LA

Parameter	Description
Live Line Threshold 2000...15,000 V Default 2000 V	Determines the voltage level at which a terminal is considered to be live. This value is used to generate Load/Source On/Off events that trigger LA. It must be the same value for all devices in a LA scheme. Typical value is 2000 V **setVUE: System Status Menu → Phase Voltage and Power Flow flexVUE**: Engineer Menu > Configuration Menu > System Settings > Network Parameters.
Supply Timeout 0.1...100 s Default 4 s	Determines the time between detecting a change of terminal live/dead status and generating the Supply On/Off event. It is this event that triggers the start of the LA timer and must be set to the same value in all devices in a LA scheme. The value of this parameter is set by utility practices. A value of 0.5 to 5.0 s is typical. **setVUE: System Status Menu > Phase Voltage and Power Flow flexVUE**: Engineer Menu > Configuration Menu > System Settings > Network Parameters.
Coordination Time (T1)	There has to be a delay between the actions of each of the LA devices. For example: the Mid-Point device must change its protection group before the Tie device closes. This is known as the coordination time. A typical time is 10 s. Minimum recommended time is 5 s.
Single Shot Reset Time (2 x T1)	The single shot facility is used by LA to force one shot to lockout in the Mid-Point and Tie devices prior to the Tie closing onto a faulted feeder. The Single Shot timer must be set longer than the LA coordination time (T1), twice as long is recommended. **setVUE: Protection Menu > Protection Setting 2 flexVUE**:Engineer Menu > Protection Menu > Protection Trip Settings > Single Shot > Reset.
Maximum Sequence Time (T2)	LA must only take control after there is no possibility of the supply being restored by an auto reclose from a device. Therefore the LA Time must be longer than the maximum time the device will take to trip to lockout. This is called the Maximum Sequence Time. Maximum Sequence time is determined by the protection settings and the expected fault levels. It must include the Time to Trip and the Reclose time for each reclose in a sequence. To limit the Time to Trip it may be desirable to set a maximum time to trip. For example: a typical reclose sequence has an instantaneous trip, a 1 s dead time followed by a second inverse time trip with a max time of 5 s. This sets the Maximum Sequence Time to be approximately 6 s. If there is a possibility of low level faults with long trip time (perhaps on fused spur lines) then these can take longer than the Maximum Sequence Time provided that they do not reduce the system voltage to a level where Loss of Supply events occur.
ACO Time (T1 + T2)	Determines the period of time that power (greater than 50 kW) must flow in the reversed direction before an automatic change of protection groups takes place. Used in the Mid-Point device to change protection settings when restoring the normal configuration, it is also used when power flows to the alternate source in a closed Tie device and LA is turned off. In a LA scheme this must be long enough to allow an auto reclose sequence to finish. Therefore it must be longer than the Maximum Sequence Time (T2). A time of T2 plus the Coordination Time is recommended.
Live Load Blocking On/Off	This setting takes priority over LA closing and must be turned Off when LA is used. Factory default: OFF
LA Available	Enables or disables the entire LA facility. This must be set to Available in all devices used in the LA scheme. Factory default is Not Available.
Dead Time Detection On/Off (This mode is only for Tie switchgear).	Turns the LA Dead Time function ON or OFF. By default, Dead Time is On for a Tie on an AS and Off or a Tie on an ACR.
Forward Dead Time Reverse Dead Time	This value is used to determine the allowable upstream device dead time for forward or reverse Tie reconfiguration. This is a value for example 25 s ± a margin (see below). Factor default: 25.0 s
Forward Margin ± Reverse Margin ±	The margin is used with the Dead Time values above. This value is typically not more than the trip time of the upstream devices. Factory default: 2.0 s
Device Type	Determines whether the device operates as a Feeder, Mid-Point or Tie ACR device or a Tie or Feeder sectionaliser device. Range: Feeder, Mid-Point, Tie Factory default: Tie
Power Direction	Designates which terminals of the switchgear are the source and load sides in normal configuration. For the Feeder device this in only important if auto restore is used. For the Mid-Point device this affects the selection of the protection group. Which is set automatically by the direction of the power flow when the Tie device is closed. Therefore if the direction parameter is not right the wrong protection group will be active. For the Tie device this affects the protection group selection as for the Mid-Point device and, in addition will affect the Tie Restore One Way direction. If wrongly set, then the Tie will operate for loss of supply on the wrong side. This parameter can only be set after field installation when the switchgear orientation is known. Range: Source 1 – Load 2 or Source 2 – Load 1 on the N Series and Source I – Load X or Source X – Load I on the PMSet U, PMSet UR and RL Series Factory defaults are: Source 1 – Load 2 for the N Series Source I – Load X for the PMSet U, PMSet UR and RL Series.
Loop Auto Time (Activation Delay) (LA)	Determines the delay after a Supply On/Off event before the LA program takes action. The same time out value is used both when supply is lost and during an Auto Restore operation. Range: 3 to 1800 s Factory default: 30 s
Auto Restore Available	Enables or disables the Auto Restore facility. This is a security feature that helps to ensure the Auto Restore features cannot be turned on unless this field is first set to Auto Restore Available. The network must be able to operate closed if Auto Restore is used. Range: Available, Not Available Factory default: Auto Restore Not Available
Tie Restore	Only applies to a Tie device. This field is only displayed if Device Type is set to Tie ACR. This field sets whether a Tie ACR reconfigures supply in both directions, or just from Source to Load. Set Tie Restore Both Ways if you want to restore symmetrically across the Tie device. Range: One Way, Both Ways Factory default: Tie Restore One Way
LA On/Off	Turns the LA function On or Off. Range: LA On, LA Off Factory default: LA Off
Arming Mode (configurable via WSOS only)	Default mode causes LA to operate only when a loss of voltage occurs after there has been Live voltage whilst LA is active. Alternate mode can be used by a Tie device to allow LA to respond to logic conditions that exist when LA is turned on. For example, if LA is turned On while the Tie device is live on the source and dead on the load, the LA timer would start. Alternate mode may avoid the problem of manually closing a Tie while an upstream device is mid sequence. A Tie device with Live/Dead condition is closed while the upstream device is in the middle of a reclose sequence, causing potentially 2 out of phase networks to be connected. (Using the Alternate mode resolves this as the LA time of the Tie is always configured to be greater than the sequence time T2 of the upstream devices sequences). Warning: alternate mode may cause turning LA on to close the switch before any loss of supply events are generated.
Pickup (configurable via WSOS only)	Set to Blocks Trigger by default. This causes LA to ignore any loss of supply events while still in pickup. The default is changed to Allows Trigger. This causes LA to ignore any loss of supply events while still in pickup (also dependent on fault reset time, see below). Changing Pickup to Allows Trigger will allow LA to process loss of supply events during pickup. This would helps to ensure protection operations can complete a protection sequence with auto recloses at the same time as allowing LA to operate on Loss of Supply triggers i.e. without restoring power in a temporary fault situation. This mode is selectable only for Feeder and Mid-Point devices.
LOP/LA Linked/Not Linked	If set to Linked, turning LOP Off will turn LA Off and vice versa. (Only available for Classic LA)
Under Frequency Pause/Abort of Restoration (Tie only)	When enabled, this feature will either: Pause the LA Activation Delay timer or Abort Tie restoration by setting LA to Off If an under frequency condition is detected on the LIVE side of an OPEN switch during a Tie restoration.
Frequency Low At (Tie only)	The frequency at which the LA Activation Delay timer is paused. If the frequency is less than or equal to Frequency Low At contiguously for the Detection Abort Time period then restoration is aborted by setting LA Off.
Frequency Normal At (Tie only)	The tie live side frequency threshold at which the paused LA Activation Delay is resumed after the live side frequency has been greater than or equal to the Frequency Normal At threshold and the Reset time period has elapsed.
Detection Abort Time (Tie only)	If a contiguous Frequency Low At condition exceeds the Detection Abort Time period, then restoration is aborted by setting LA to Off.
Reset Time (Tie only)	Subsequent to a Frequency Low At condition, if the live side frequency reverts to being greater than or equal to the Frequency Normal At threshold for the Reset Time period then the paused LA Activation Delay time is resumed. If the live side frequency falls to less than or equal to Frequency Low At threshold during the Reset Time period, then the reset timer is cleared to zero, and the Detection Abort timer is started.

Parameter

Description

Live Line Threshold

2000...15,000 V

Default 2000 V

Determines the voltage level at which a terminal is considered to be live. This value is used to generate Load/Source On/Off events that trigger LA. It must be the same value for all devices in a LA scheme.

Typical value is 2000 V

setVUE: System Status Menu → Phase Voltage and Power Flow

flexVUE: Engineer Menu > Configuration Menu > System Settings > Network Parameters.

Supply Timeout

0.1...100 s

Default 4 s

Determines the time between detecting a change of terminal live/dead status and generating the Supply On/Off event. It is this event that triggers the start of the LA timer and must be set to the same value in all devices in a LA scheme. The value of this parameter is set by utility practices. A value of 0.5 to 5.0 s is typical.

setVUE: System Status Menu > Phase Voltage and Power Flow

flexVUE: Engineer Menu > Configuration Menu > System Settings > Network Parameters.

Coordination Time (T1)

There has to be a delay between the actions of each of the LA devices. For example: the Mid-Point device must change its protection group before the Tie device closes. This is known as the coordination time. A typical time is 10 s. Minimum recommended time is 5 s.

Single Shot Reset Time (2 x T1)

The single shot facility is used by LA to force one shot to lockout in the Mid-Point and Tie devices prior to the Tie closing onto a faulted feeder. The Single Shot timer must be set longer than the LA coordination time (T1), twice as long is recommended.

setVUE: Protection Menu > Protection Setting 2

flexVUE:Engineer Menu > Protection Menu > Protection Trip Settings > Single Shot > Reset.

Maximum Sequence Time (T2)

LA must only take control after there is no possibility of the supply being restored by an auto reclose from a device. Therefore the LA Time must be longer than the maximum time the device will take to trip to lockout. This is called the Maximum Sequence Time.

Maximum Sequence time is determined by the protection settings and the expected fault levels. It must include the Time to Trip and the Reclose time for each reclose in a sequence. To limit the Time to Trip it may be desirable to set a maximum time to trip.

For example: a typical reclose sequence has an instantaneous trip, a 1 s dead time followed by a second inverse time trip with a max time of 5 s. This sets the Maximum Sequence Time to be approximately 6 s.

If there is a possibility of low level faults with long trip time (perhaps on fused spur lines) then these can take longer than the Maximum Sequence Time provided that they do not reduce the system voltage to a level where Loss of Supply events occur.

ACO Time (T1 + T2)

Determines the period of time that power (greater than 50 kW) must flow in the reversed direction before an automatic change of protection groups takes place.

Used in the Mid-Point device to change protection settings when restoring the normal configuration, it is also used when power flows to the alternate source in a closed Tie device and LA is turned off.

In a LA scheme this must be long enough to allow an auto reclose sequence to finish. Therefore it must be longer than the Maximum Sequence Time (T2).

A time of T2 plus the Coordination Time is recommended.

Live Load Blocking On/Off

This setting takes priority over LA closing and must be turned Off when LA is used.

Factory default: OFF

LA Available

Enables or disables the entire LA facility.

This must be set to Available in all devices used in the LA scheme.

Factory default is Not Available.

Dead Time Detection On/Off

(This mode is only for Tie switchgear).

Turns the LA Dead Time function ON or OFF.

By default, Dead Time is On for a Tie on an AS and Off or a Tie on an ACR.

Forward Dead Time

Reverse Dead Time

This value is used to determine the allowable upstream device dead time for forward or reverse Tie reconfiguration. This is a value for example 25 s ± a margin (see below).

Factor default: 25.0 s

Forward Margin ±

Reverse Margin ±

The margin is used with the Dead Time values above. This value is typically not more than the trip time of the upstream devices.

Factory default: 2.0 s

Device Type

Determines whether the device operates as a Feeder, Mid-Point or Tie ACR device or a Tie or Feeder sectionaliser device.

Range: Feeder, Mid-Point, Tie

Factory default: Tie

Power Direction

Designates which terminals of the switchgear are the source and load sides in normal configuration.

For the Feeder device this in only important if auto restore is used.

For the Mid-Point device this affects the selection of the protection group. Which is set automatically by the direction of the power flow when the Tie device is closed. Therefore if the direction parameter is not right the wrong protection group will be active.

For the Tie device this affects the protection group selection as for the Mid-Point device and, in addition will affect the Tie Restore One Way direction. If wrongly set, then the Tie will operate for loss of supply on the wrong side.

This parameter can only be set after field installation when the switchgear orientation is known.

Range: Source 1 – Load 2 or Source 2 – Load 1 on the N Series and

Source I – Load X or Source X – Load I on the PMSet U, PMSet UR and RL Series

Factory defaults are: Source 1 – Load 2 for the N Series

Source I – Load X for the PMSet U, PMSet UR and RL Series.

Loop Auto Time (Activation Delay) (LA)

Determines the delay after a Supply On/Off event before the LA program takes action. The same time out value is used both when supply is lost and during an Auto Restore operation.

Range: 3 to 1800 s

Factory default: 30 s

Auto Restore Available

Enables or disables the Auto Restore facility. This is a security feature that helps to ensure the Auto Restore features cannot be turned on unless this field is first set to Auto Restore Available.

The network must be able to operate closed if Auto Restore is used.

Range: Available, Not Available

Factory default: Auto Restore Not Available

Tie Restore

Only applies to a Tie device.

This field is only displayed if Device Type is set to Tie ACR. This field sets whether a Tie ACR reconfigures supply in both directions, or just from Source to Load.

Set Tie Restore Both Ways if you want to restore symmetrically across the Tie device.

Range: One Way, Both Ways

Factory default: Tie Restore One Way

LA On/Off

Turns the LA function On or Off.

Range: LA On, LA Off

Factory default: LA Off

Arming Mode

(configurable via WSOS only)

Default mode causes LA to operate only when a loss of voltage occurs after there has been Live voltage whilst LA is active.

Alternate mode can be used by a Tie device to allow LA to respond to logic conditions that exist when LA is turned on. For example, if LA is turned On while the Tie device is live on the source and dead on the load, the LA timer would start.

Alternate mode may avoid the problem of manually closing a Tie while an upstream device is mid sequence. A Tie device with Live/Dead condition is closed while the upstream device is in the middle of a reclose sequence, causing potentially 2 out of phase networks to be connected.

(Using the Alternate mode resolves this as the LA time of the Tie is always configured to be greater than the sequence time T2 of the upstream devices sequences).

Warning: alternate mode may cause turning LA on to close the switch before any loss of supply events are generated.

Pickup

(configurable via WSOS only)

Set to Blocks Trigger by default. This causes LA to ignore any loss of supply events while still in pickup.

The default is changed to Allows Trigger. This causes LA to ignore any loss of supply events while still in pickup (also dependent on fault reset time, see below).

Changing Pickup to Allows Trigger will allow LA to process loss of supply events during pickup. This would helps to ensure protection operations can complete a protection sequence with auto recloses at the same time as allowing LA to operate on Loss of Supply triggers i.e. without restoring power in a temporary fault situation.

This mode is selectable only for Feeder and Mid-Point devices.

LOP/LA Linked/Not Linked

If set to Linked, turning LOP Off will turn LA Off and vice versa. (Only available for Classic LA)

Under Frequency Pause/Abort of Restoration (Tie only)

When enabled, this feature will either:

Pause the LA Activation Delay timer

Abort Tie restoration by setting LA to Off

If an under frequency condition is detected on the LIVE side of an OPEN switch during a Tie restoration.

Frequency Low At (Tie only)

The frequency at which the LA Activation Delay timer is paused. If the frequency is less than or equal to Frequency Low At contiguously for the Detection Abort Time period then restoration is aborted by setting LA Off.

Frequency Normal At (Tie only)

The tie live side frequency threshold at which the paused LA Activation Delay is resumed after the live side frequency has been greater than or equal to the Frequency Normal At threshold and the Reset time period has elapsed.

Detection Abort Time (Tie only)

If a contiguous Frequency Low At condition exceeds the Detection Abort Time period, then restoration is aborted by setting LA to Off.

Reset Time (Tie only)

Subsequent to a Frequency Low At condition, if the live side frequency reverts to being greater than or equal to the Frequency Normal At threshold for the Reset Time period then the paused LA Activation Delay time is resumed.

If the live side frequency falls to less than or equal to Frequency Low At threshold during the Reset Time period, then the reset timer is cleared to zero, and the Detection Abort timer is started.