Setting and troubleshooting of Basler BE1-27/59 voltage relay

Basler BE1-27/59 Voltage Relay Setting and Field Troubleshooting Guide

In the power system, abnormal voltage (under voltage or over voltage) is one of the main causes of motor burnout, transformer overexcitation, misoperation of automatic transfer switches, and disconnection of distributed power sources. The Basler BE1-27 (undervoltage), BE1-59 (overvoltage), and BE1-27/59 (undervoltage/overvoltage combination) series solid state relays, with wide range tuning, flexible time characteristics (instantaneous, timed, inverse time), and high anti-interference ability, have long served industrial distribution, power plants, and cogeneration grid points. However, on-site engineers often encounter problems such as incorrect conversion of setting values, improper selection of time curves, and unfamiliarity with testing procedures when commissioning or replacing old relays. This article is based on the complete technical manual of this series, systematically sorting out its application scenarios, key parameters, panel operations, testing and calibration, and typical fault handling, providing relay maintenance personnel with an engineering manual that can be checked and used immediately.

Overview of Product Series and Selection

BE1-27 is an undervoltage relay, BE1-59 is an overvoltage relay, and BE1-27/59 is an undervoltage/overvoltage combination relay. All three are solid-state and use a drawer style S1 chassis with a panel containing potentiometers, indicator lights, and test buttons. The model is defined by the "Style Number" encoding and includes the following options:

Voltage detection range: Range 2 (55-160V, suitable for 120V/69V systems), Range 3 (110-320V, suitable for 240V/208V/277V systems), Range 4 (1-40V, used for open delta zero sequence voltage detection).

Time characteristics: instantaneous (I), timed limit (D, adjustable from 0.1 to 9.9 seconds), inverse time limit (short/medium/long curves).

Output contact configuration: normally open/normally closed, independent or combined.

Auxiliary power supply: DC 24V/48V/125V or AC 120V/240V wide range input.

When selecting, it is necessary to clarify: the protected object (motor, transformer, busbar), voltage level, whether it needs to have both undervoltage and overvoltage functions, and whether it needs instantaneous and delayed two-stage protection (such as allowing short-term undervoltage during motor start-up).

Typical application scenarios and tuning logic

2.1 Motor undervoltage protection

When the motor starts, the bus voltage may briefly drop. If the drop amplitude is too large or the duration is too long, the motor will not be able to accelerate to the rated speed, resulting in overcurrent heating. BE1-27 can be set with a fixed time limit (such as 0.5-2 seconds) or an inverse time limit (the deeper the drop, the faster the action), and will only trip when the voltage remains below the set value to avoid starting impact misoperation.

2.2 Automatic Transfer Switch (ATS) Voltage Monitoring

In a dual power supply system, BE1-27 detects the loss or low voltage of the main power supply and issues a switching command after a delay; BE1-59 monitors whether the backup power supply voltage has returned to the normal range to prevent reclosing on live equipment. The manual states that undervoltage relays are commonly used for "trip transfer" logic, while overvoltage relays are used for "normal recovery" supervision.

2.3 Grid Connection Interface Protection (Cogeneration)

When a distributed power source (such as a gas turbine) is connected in parallel with the power grid, if the circuit breaker on the grid side trips, the distributed power source may operate independently with load, causing the risk of asynchronous reclosing. BE1-27 monitors the line voltage. If the line is still live (maintained by distributed power sources), it will be locked and reconnected to prevent grid impact. Meanwhile, BE1-59 can detect overvoltage caused by capacitor switching and promptly cut off distributed power sources.

2.4 Transformer overexcitation protection

When a transformer operates under overvoltage or low frequency, the magnetic flux density of the iron core increases, causing a sharp increase in excitation current and overheating of the winding. BE1-27/59 can set the overvoltage setting (such as 110% rated) and cooperate with inverse time characteristics to delay tripping during overexcitation, avoiding transformer damage.

2.5 Grounding Fault Detection (Open Triangle Method)

In a three-phase three wire system, if configured as a grounded star open delta PT, the zero sequence voltage increases in the event of a single-phase grounding fault. BE1-59 (or BE1-27/59 overvoltage unit) is connected to an open delta winding and can detect grounding faults in low current grounding systems through sensitive tuning (range 4, 1-40V).

Interpretation of Key Electrical Parameters

3.1 Voltage detection input

Range 2: 55-160Vac (nominal 120V system), with a continuous overload capacity of 1.5 times.

Range 3: 110~320Vac (nominal 240V/277V system).

Range 4:1-40Vac (dedicated for zero sequence voltage).

Internally, a step-down transformer is used for isolation, with extremely low power consumption (<1VA).