BHEL UN0661AV1 DVR Card (Part No. 69203GB1AA) Turbine Control Module

1. Product Description

UN0661AV1 with factory part number 69203GB1AA is a DVR (Digital Voltage Regulator) rack plug-in PCB module manufactured by BHEL (Bharat Heavy Electricals Limited), dedicated for heavy-duty steam turbine and gas turbine Speedtronic control racks. It is a single-slot vertical VME-format card with full conformal coated circuit board to withstand dust, high humidity and corrosive flue gas environments inside power plant control cabinets. This module acts as the core voltage regulation signal processing unit for generator excitation and turbine governor closed-loop control, compatible with simplex and triple redundant TMR turbine protection architectures. It receives analog voltage feedback signals from generator PT transformers, executes high-speed voltage loop PID calculation, and outputs regulated drive signals to excitation thyristor rectifiers. The rear edge is equipped with multi-row high-density gold finger bus connectors for rack backplane communication, while the front metal panel integrates status LED indicators, test terminals and dual ejector latches supporting hot-swap maintenance without full rack power shutdown. It operates on 24VDC rack power supply and complies with industrial EMC, CE power generation safety standards.

2. Core Product Functions

• Generator stator voltage sampling and conditioning: process PT secondary voltage signals to measure actual terminal voltage of synchronous generators
• High-speed AVR automatic voltage regulation closed-loop control, adjustable PID gain parameters for stable generator voltage under grid load fluctuation
• Excitation thyristor firing pulse generation, output precise trigger signals to adjust excitation current and maintain rated generator voltage
• Multi-stage overvoltage/undervoltage fault detection, trigger generator protection trip logic when voltage exceeds preset safety thresholds
• Complete circuit self-diagnosis: detect PT signal open/short circuit, internal PCB power failure, backplane bus communication loss and pulse output circuit damage
• TMR redundant cross-checking: synchronize voltage measurement data with two other identical UN0661AV1 modules in triple redundant racks to eliminate single-card measurement deviation
• Galvanic isolation between high-voltage PT field wiring and internal control logic to block EMI interference from generator transformers and high-voltage switchgear
• Transmit real-time voltage value, excitation output and fault codes to rack main CPU via backplane bus, upload trend and alarm data to plant DCS monitoring system

3. Application Scenarios

• Coal-fired thermal power plant steam turbine generator excitation control cabinets
• Combined cycle gas turbine power plant generator AVR voltage regulation systems
• Hydroelectric power station large synchronous generator voltage control racks
• Refinery and petrochemical on-site power generation turbine generator protection control panels
• Heavy industry captive power plant turbine redundant TMR safety control systems

4. Common Troubleshooting & Typical Issues

• Persistent PT Signal Loss Fault Alarm

  Causes: Damaged potential transformer secondary wiring, loose terminal block connections, burnt internal signal isolation circuit on DVR card. Solutions: Inspect PT cable continuity, re-tighten all field wiring terminals, test and replace damaged signal conditioning channels.

• Unstable Generator Voltage Hunting & Fluctuation

  Causes: Improper PID tuning parameters on UN0661AV1, unshielded PT signal cables, severe EMI interference from nearby high-voltage equipment. Solutions: Optimize AVR loop proportional/integral gains, install double-shielded twisted pair wiring and connect cable shielding to cabinet protective ground.

• TMR Voting Discrepancy Alarm in Redundant Rack

  Causes: Uneven signal attenuation of three PT measurement loops, inconsistent calibration offsets among three UN0661AV1 cards. Solutions: Synchronize calibration parameters for all three DVR modules, unify length and shielding specification of PT field cables.

• Module FAIL LED Constantly Illuminated, Unrecognized by Main Controller

  Causes: Dirty backplane gold finger contacts, unstable 24VDC rack power supply, corrupted on-board firmware. Solutions: Clean PCB gold fingers with anti-static lint-free cloth, stabilize rack DC power voltage, reload factory firmware or replace faulty UN0661AV1 module.

• Excitation Pulse Output Failure, Generator Voltage Drifts Out of Range

  Causes: Internal pulse driver circuit burnout on DVR card, open circuit of thyristor trigger wiring. Solutions: Measure trigger pulse output at front test terminals, repair broken excitation wiring or replace defective module.