3.2 Time characteristics and curves
Instantaneous: Response time<50ms (under voltage) or<80ms (over voltage), used to immediately cut off severe voltage abnormalities.
Time limit: adjustable from 0.1 to 9.9 seconds (step size 0.1 seconds), suitable for coordination with lower level protection.
Inverse time limit: Provide short, medium, and long curves (see manual figures 3-2 to 3-7), with action time decreasing with voltage deviation and better matching with equipment thermal capacity.
3.3 Output contact capacity
DC resistance: 1.0A @ 125VDC; DC inductance: 0.3A @ 125/250VDC (L/R=0.04).
Communication: 7.5A @ 208VAC.
Short time on-off capability: 30A/0.2s (200Vdc).
Attention: Current type target indication requires a circuit current of ≥ 200mA to trigger.
3.4 Auxiliary power supply
Table 1-1 lists various types of power sources (K/J/L/Y/Z), covering DC 24-280V and AC 120-240V, suitable for different on-site power conditions. When the power supply loses power, the power status contact (normally closed) closes the alarm.
Front panel control and indicator light instructions
The panel layout (Figure 2-1) includes:
Undervoltage setting potentiometer (A): Set the delayed undervoltage action value.
Undervoltage delay dial (B): The timing limit is set to 0.0 to 9.9 seconds; Inverse time selection curve slope.
Instantaneous undervoltage setting (C): Independently set the instantaneous undervoltage action value.
Overvoltage setting (D), overvoltage delay (E), overvoltage instantaneous (F): same as the undervoltage side.
Power indicator light (G): red LED.
Target reset button (H): Reset the electronic latch LED target.
Overvoltage/undervoltage indicator lights (I, L): Indicates that the corresponding function has been activated.
Target indicator (J): The red LED is locked when the trip output is triggered.
Output test button (K): The output relay can be manually operated by pressing it with an insulating rod for circuit verification.
Functional principle description
After internal PT voltage reduction, low-pass filtering (suppressing>226Hz noise), and full wave rectification, the system voltage is compared with the reference voltage of each potentiometer. When the voltage exceeds the overvoltage threshold or falls below the undervoltage threshold, the corresponding comparator triggers a timer. If the duration reaches the delay setting, the drive output relay will trip. The instantaneous function bypasses the timer and acts directly.
Priority: In BE1-27/59, the undervoltage function takes priority over the overvoltage function (when both are met, undervoltage output takes priority).
Inverse time curve: Figures 3-2 to 3-7 in the manual show six curves for undervoltage (short/medium/long) and overvoltage (short/medium/long), with the horizontal axis representing the percentage difference between voltage and setting value and the vertical axis representing the action time. Users can select one of the different curve families through the delay dial.
Key points for on-site installation and wiring
Chassis: S1 semi embedded or protruding installation, dimensions are shown in Figure 4-1 to 4-12, and the shell must be grounded with ≥ 12AWG copper wire (terminal "GND").
AC connection: The typical wiring is shown in Figure 4-16. The voltage detection input is connected to the PT secondary side, paying attention to phase and polarity (for open delta mode).
DC control circuit: Figure 4-17, the output contacts are connected in series to the trip coil or alarm circuit.
Caution: If the connection plug is unplugged, the relay will lose its protective function and must be operated under stable conditions. Before conducting insulation testing, it is necessary to remove the plug to avoid damaging the internal circuit.

On site testing and calibration steps (excerpted from Section 5 of the manual)
High precision variable frequency voltage source (frequency stability better than 0.00002Hz, phase noise<90dB), oscilloscope or timer are required for testing.
7.1 Startup value (Pickup) test
Regarding Scope 3 (120V system, undervoltage):
Turn all undervoltage settings to the lowest and overvoltage settings to the highest.
Apply voltage to the rated value (such as 120V).
Slowly reduce the voltage, observe the undervoltage indicator light and record the voltage - it should be 54-56Vac (45% to 47% of the rated 120V, set by the manufacturer).
Then turn the undervoltage setting to the highest, reduce the pressure, and record the action value - it should be between 156.8 and 163.2 Vac (near the upper limit of range 3). This step verifies the setting range.
Similarly, for overvoltage testing, boost the voltage to the operating point (range 3 overvoltage upper limit is approximately 156.8~163.2Vac).
Range 4 (1-40V) is used for grounding detection, and the test voltage is low, requiring a adjustable voltage source.
7.2 Time Delay Verification
Set the delay dial to "00" (instantaneous), apply step voltage (under voltage or over-voltage jump), and measure the output action time to be ≤ 50ms (instantaneous).
Set the delay dial to "01" (0.1 seconds), and the timed limit type should measure 0.05-0.15 seconds; If set to "99" (9.9 seconds), the measured time is 9.70-10.10 seconds.