Basler PRS 250 Synchronous Relay Maintenance and Replacement Guide

2.6 Environmental and Mechanical Tolerance

Working temperature: -40 ° C to+70 ° C (suitable for outdoor cabinets and extremely cold areas)

Vibration: 1.3G (5-26Hz) to 5G (52-260Hz)

Impact: 15G (in any direction)

Size: 7.12 "x 7.10" x 3.31 "(approximately 181mm x 180mm x 84mm), standard panel mounting or DIN rail (requires adapter bracket)

Weight: Net weight 6.5 pounds (approximately 2.95kg), relatively heavy, pay attention to the load-bearing capacity of the guide rail during installation.

Typical application scenarios and replacement compatibility

3.1 Replace old style electromechanical synchronous relays

Many old distribution boards use GE type IJS or Westinghouse type ANL synchronous relays, which have low precision, easy contact wear, and difficult tuning for electromagnetic products. PRS 250 provides more stable solid-state logic and adjustable phase angle and slip limits, but it should be noted that the original relay may include undervoltage/overvoltage protection function, while PRS 250 only allows voltage (6.6%) and does not have independent undervoltage lockout - if undervoltage protection is required, an additional undervoltage relay needs to be configured.

3.2 Replace Woodward 2301 series synchronization module

The synchronization check function that comes with speed controllers such as Woodward 2301 is often integrated into the control card. Once the card is discontinued, the separated synchronous relay becomes an economical alternative. At this point, it is necessary to connect the "allow" contact of PRS 250 in series into the closing circuit, and separate the "speed increase/decrease" signal of the governor from the relay, without interfering with the speed control action - PRS 250 is only used for passive verification.

3.3 Coordination with automatic quasi synchronization device

For situations where automatic quasi synchronization has been configured (such as Basler DECS-250 excitation system), PRS 250 can be used as a backup redundancy and connected in series in the closing circuit to achieve dual safety. Even if the automatic device mistakenly closes due to software failure, PRS 250 can still check again based on the hard wired parameters.

On site installation and parameter tuning steps

4.1 Key points for wiring inspection

Voltage input: Confirm that the secondary side voltage of the generator PT corresponds to the terminal (G-GEN) and the bus PT corresponds to the terminal (B-BUS). The same phase must be used (such as phase A and phase A), otherwise the phase difference remains constant at 120 ° or 240 °, and the relay will always close.

Common terminal: The voltage common terminal (COM) must be connected to the neutral points of two PTs and ensure equal potential.

Output contact: Confirm that the contact capacity is sufficient based on the type of closing circuit (AC or DC). If it is a DC operation, it is recommended to use a "normally open" terminal connected in series between the closing button and the closing coil.

Shielding and grounding: The voltage signal line uses shielded twisted pair cables, and the shielding layer is grounded at one end to the control cabinet ground bar to avoid high-frequency interference affecting zero crossing detection.

4.2 Phase angle window setting method

When there is no dedicated phase meter, the "anti synchronization" method can be used:

Make the generator and bus voltage roughly equal, with a frequency slightly higher than the bus (forward slip);

Adjust the phase potentiometer to the minimum (0 °), observe the relay indicator light (if any) or use a multimeter to measure the contact continuity;

When the frequency difference gradually decreases to near zero, if the contact is attracted near the voltage zero crossing, it indicates that the phase window is correct. If a larger advance amount (compensating for circuit breaker time) is required, gradually increase the angle until the impact current is minimized when closing.

4.3 Slip frequency verification

Measure the generator frequency fG and bus frequency fB using a frequency meter, and the difference must be less than 0.5Hz. If it is higher than this value, adjust the steady-state speed regulation rate of the prime mover governor (such as changing the integration time of the Woodward actuator). If the slip cannot be reduced on site, it can only be replaced with a relay that supports higher slip (such as 1Hz), but PRS 250 does not have this option.

4.4 Voltage matching adjustment

If the voltage difference between the generator and the bus exceeds 6.6%, the voltage setpoint of the AVR needs to be adjusted (such as the "VOLT" potentiometer of Basler DECS-100). Note that the bandwidth is a percentage based on the bus, and when the bus fluctuates, the allowed absolute deviation also changes synchronously, with good dynamic tracking.

Common fault phenomena and systematic troubleshooting

Fault 1: The relay has never closed (allowing the signal to remain disconnected)

Possible reasons:

Voltage deviation exceeds 6.6% (check two PT output values and measure with a multimeter in AC mode)

Frequency difference greater than 0.5Hz (check the speed regulator and observe the fluctuation of the frequency meter)