Test Plan for the Line-Entry Switch Standby Automatic Transfer (Line-Entry Standby Transfer)

Front-end settings: activate the backup supply and the total supply soft pressure plate; set the control word KG1.1=1; enable the incoming-line backup supply mode. Description: switch position input logic: high level = input set; no signal input = input reset.

I. Charging Test (Charging will commence only when all conditions are simultaneously satisfied)

1. Switch position conditions

·Line 2 backup, Line 1: 1DL and 3DL in the combined position; 2DL in the split position, with corresponding input/output status matching

·Line 1 – Backup Line 2: 2DL and 3DL in the combined position; 1DL in the split position, with corresponding input/output status matching

2. Busbar voltage conditions

Positive-sequence voltage is applied to both busbars; the voltages at Busbar I and Busbar II are both greater than the voltage-setpoint Udz2, indicating that the busbars are energized.

3. Backup incoming-line voltage condition (KG2.0 = 0; verify that the backup incoming line has voltage)

·Main feed-in line 2, backup feed-in line 1: the voltage on the backup feed-in line is greater than the voltage-setpoint Udz3.

·Main feed-in line 1, backup feed-in line 2: the voltage on the backup feed-in line is greater than the voltage-setpoint Udz3.

4. Charging Completion Determination

When all the above conditions are met, after a 10s charging period, the standby charging indicator will remain illuminated, and the remote signal "Standby Charging Full" will be set to the ON position.

II. Discharge Test (satisfy any one of the following conditions; immediate discharge upon activation of the backup)

1. Abnormal discharge at the standby switch position

·Line 2 backup line 1: 2DL changes to the closed position

·Main feed 1 → Backup feed 2: 1DL changes to the closed position

2. No-voltage delayed discharge for the backup incoming line (KG2.0=0)

Line 2 backup, Line 1: when the voltage on Line 2 falls below the voltage threshold Udz3 and remains so for 60s, discharge occurs

Line 1 → Backup Line 2: If the voltage on Line 1 falls below the voltage threshold Udz3, discharge after a continuous duration of 60s.

Manually trip the incoming line switch: when incoming line 2 is the backup for incoming line 1, manually trip 1DL; when incoming line 1 is the backup for incoming line 2, manually trip 2DL, and then activate the backup power supply.

3. External interlock signal discharge

The standby feeder's total locking input/exit has an input and a display indicating the closed position; the standby feeder is energized.

III. Movement Test

Operating Condition 1: Busbar voltage loss; no current in the incoming line; start-up and transfer of the backup unit

1.Line 2 backup, Line 1: neither Busbar I nor Busbar II is energized; the incoming line current is below the no-current setpoint Idz1; the incoming line is energized (KG2.0=0). After a T1 delay, output breaker 1DL trips; once it is confirmed that 1DL has opened and the incoming line remains energized, breaker 2DL is closed after a T6 delay.

2.Line 1 incoming, backup Line 2 incoming: neither Busbar I nor Busbar II is energized; the incoming line current is below the no-current setpoint Idz2; the incoming line is energized (KG2.0=0). After a T2 delay, the output trips via 2DL; once it is confirmed that 2DL has opened and that the incoming line remains energized, 1DL is closed after a T6 delay.

Operating Condition 2: Transformer protection trips and activates the backup unit

1.Line 2 backup, Line 1: the input for the transformer protection operation receives a signal; 1DL and 3DL are set to trip position, the line voltage is present, the control word is activated, and 2DL closes after the T6 delay.

2.Line 1 → Backup Line 2: The transformer protection operation generates a signal at the input; 2DL and 3DL are set to the trip position; the incoming line is energized; the control word is activated; and 1DL closes after the T6 delay.

Note: If the protection operation signals from both transformers are connected to the main lockout input/exit for the backup switching-over function, this test need not be performed.

Operating Condition 3: Backup acceleration function (KG2.7=1, backup acceleration activated)

Once the backup protection is activated, if the corresponding operating switch is already in the trip position, the backup protection logic bypasses the trip delay and directly determines that the switch has tripped; after a T6 delay, the backup switch is then closed.

·Line 2 backup to Line 1: 1DL has already tripped; without trip delay, T6 closes at the designated point to 2DL

·Line 1 → Backup Line 2: 2DL has already tripped; without a trip delay, T6 closes at the designated point and energizes 1DL.

💡 Complete Summary

The three-step procedure for standby switching and commissioning: 1. Verify the switching method, pressure plates, and control words; 2. Gradually satisfy each condition to achieve stable charging; 3. Conduct a full-operation test simulating voltage loss, protection tripping, and accelerated operating conditions. Once you have mastered this process, commissioning the incoming-line standby switching will become a completely independent task.