Basler Electric 90-88800-102 PRS-250 Veri-Sync Relay

The Basler Electric PRS‑250 Veri‑Sync relay is a solid‑state synchronism‑checking device designed to prevent asynchronous closure of circuit breakers when paralleling two AC power sources. It is commonly used in generator paralleling, bus transfer, and co‑generation applications. The relay continuously monitors the voltage magnitude, phase angle, and frequency difference between two live sources and issues a permissive signal only when all conditions are within preset limits. This ensures that breakers are closed at the optimal moment, minimizing mechanical stress and electrical transients.

Core Functionality

The PRS‑250 operates by comparing the voltage and phase of the incoming source (e.g., a generator) against a reference bus. The relay has independent adjustable settings for voltage match (typically 5‑20% of nominal), phase angle (1‑20 degrees), and slip frequency (0.05‑0.5 Hz). When all parameters fall within the selected windows for a user‑defined dwell time, the relay closes its output contact, enabling the breaker close circuit. If any parameter drifts outside the window, the output is blocked, preventing unsafe synchronization.

Key Features

This relay features a high‑impedance input circuit that minimizes burden on voltage transformers. It includes a built‑in test pushbutton to simulate acceptable synchronism conditions for functional testing. The front panel provides LED indicators for source presence, phase match, and relay status. An adjustable time delay (0.1‑10 seconds) can be set to ensure the permissive signal is stable before closing. The relay also offers a voltage‑matching output to control automatic voltage regulators for fine‑tuning.

Technical Specifications

Input voltage: 100‑480 VAC, 50/60 Hz, single‑phase or three‑phase sensing. Pickup accuracy: ±2% for voltage, ±1 degree for phase. Slip frequency range: 0.05‑0.5 Hz. Output contact: 1 Form C (SPDT), rated 5 A at 250 VAC. Power supply: 24‑250 VDC or 120‑240 VAC built‑in. Operating temperature: –20°C to +65°C. The relay is housed in a rugged metal enclosure suitable for panel mounting.

Applications

The PRS‑250 is ideal for emergency standby generator sets, marine propulsion systems, and utility interconnections. It is also used in automatic transfer switch schemes to ensure that the backup generator is synchronized with the utility before transfer. In industrial plants with multiple generators, the relay facilitates parallel operation by providing a permissive signal to the breaker closure circuit.

Installation and Commissioning

Installation involves mounting the relay in a standard panel cutout and connecting the voltage sensing leads from the two sources. The relay provides clearly marked terminals for each input. Commissioning requires setting the voltage match, phase angle, and slip frequency values according to system requirements. A simulation mode allows testing without applying live voltage, using an external test set. Regular calibration is recommended to maintain accuracy, though the solid‑state design ensures long‑term stability.

Reliability and Standards

Basler Electric’s PRS‑250 complies with ANSI/IEEE C37.90 and IEC 60255 for protective relays. It features transient voltage suppression and surge immunity to withstand harsh electrical environments. The relay’s self‑monitoring circuitry detects internal faults and provides a fail‑safe output. With no moving parts, the PRS‑250 offers exceptional reliability and low maintenance.

Conclusion

The Basler Electric 90‑88800‑102 PRS‑250 Veri‑Sync relay is a precise and dependable solution for synchronism checking. Its adjustable parameters, robust construction, and easy integration make it a valuable component in any power system requiring safe and reliable source paralleling.