Basler BE1-87B busbar differential setting test

The total operating current (secondary value) is the sum of the excitation currents of each CT plus the relay current. If there are n CTs with the same characteristics, then

Iminsec=n × Ie '+IRI min_dec=n × Ie+IR, multiplied by the transformation ratio N to obtain the minimum operating current once.

Example (5 CTs, each 0.05A):

Iminsec=5 × 0.05+0.04=0.29AI min_dec=5 × 0.05+0.04=0.29A, with a primary value of 0.29 × 240 ≈ 70A. When the current is set to 0.5A, the corresponding primary current is 0.5 × 240=120A, and the larger one is taken, so the minimum operating current is 120A once. If the minimum fault current of the system is much greater than this, then the sensitivity is satisfied.

5. On site testing and verification

After new installation or maintenance, the relay's various functions should be tested according to the following steps.

5.1 Power Status and Basic Functions

Disconnect the power supply and ensure that terminals 11-12 (normally closed power status) are conducting.

Connect the rated power supply, the Power LED lights up, and 11-12 should be disconnected (indicating that the power supply is normal).

Disconnect the power supply, 11-12 should restore conductivity (fail safe design).

5.2 Alarm Voltage (CT OV) Test

Assuming Pickup Voltage=50V and Alarm Voltage=10% (i.e. 5V).

Apply 4.5V (90% set) for 10 seconds, and the alarm should not activate (LED not on, 13-14 not closed).

Apply 5.5V (110% setting), and the alarm action should be triggered after a few seconds (LED on, 13-14 closed). After removal, the LED will turn off (with a delay of about 1 second).

Repeatedly verify other alarm levels (20%~80%).

5.3 Voltage Pick up (SCR Trigger) Test

Set Pickup Voltage to 50V and Pickup Current to 0.25A.

Connect the voltage source to the input terminal and configure it to automatically disconnect when tripped.

When the voltage is slowly increased to about 100V (2 × 50V), the SCR should conduct, the output contacts 17-18 should close, and the Trip LED should light up. Error ± 5%.

Press Reset to reset the LED.

Assuming Pickup Voltage=100V, repeat and operate at 200V ± 4%.

Three phase models need to be tested phase by phase.

5.4 Current Pick up Test

Set the Pickup Current to 0.25A and adjust the voltage setting to 50V (to avoid voltage misoperation, but actual current testing can be triggered by short circuiting the input or applying sufficient voltage).

When the current source slowly increases from 0 to 0.25A ± 5%, the output contact closes and the Trip LED lights up.

Test each gear (0.5, 0.75,..., 2.5A) in sequence and record the action values.

5.5 Delay Test (if used)

If it is A1 (20ms delay), set the current to 3 times the set value (such as 0.75A), and measure the time from current application to contact closure, which should be within about 24.4ms (actual delay+inherent time).

A2 (2ms delay) is approximately 6.4ms.

If no delay is required, place the jumper in position 1-2 (without delay), with an action time of<7ms (1.5 times) or<5.5ms (6 times).

5.6 CT Circuit Integrity Test (Using CT Test Button)

According to the previous tuning example, assuming V_DIFF=150V and Alarm=10% (15V), calculate the required test voltage (usually using 30V or 60V range).

Connect the CT diagnostic test source to terminals 7 and 10, press the CT Test button for about 1 minute. If there is no short circuit in the CT circuit, the CT OV LED should light up and the Alarm contact should close; If the circuit is short circuited, there will be no response.

Attention: The test current should be less than the current setting value to ensure that there is no false tripping during testing. For example, when setting 0.5A, the unhealthy current tested is about 0.3A, and the safety margin is sufficient.

6. CT testing source application and security considerations

The CT test source consists of an isolation transformer and a 100 Ω series resistor, which is used to detect whether there is a short circuit in the CT circuit without exiting the protection. When the CT Test button is pressed, the test voltage (30V or 60V) is applied to the differential circuit through a resistor. If the impedance of the circuit is normal (CT parallel impedance is several hundred ohms), the voltage at the relay terminal after resistor division reaches the alarm threshold, indicating that the circuit is intact; If there is a short circuit somewhere, almost all the voltage drops across the resistor, the relay terminal voltage is insufficient, and the alarm does not operate.

Safety design: The test voltage is much lower than the SCR triggering voltage (2 × V_DIFF is usually ≥ 100V), and even if SCR is accidentally triggered, the relay will not trip due to the test current being less than the current setting value (such as 0.5A), so the testing process does not affect the safety of protection.

7. Maintenance and Storage Suggestions

BE1-87B is a solid-state relay that only requires regular (recommended annual) functional testing for daily maintenance. If stored for a long time, the internal electrolytic capacitor should be powered on for 30 minutes every year to maintain its performance. When abnormalities occur, contact the manufacturer for repair and do not dismantle or repair on site.