Bus Static Var Compensator
What is meant by 'bus voltage control' in a Bus SVC?
A Bus SVC is modeled as a variable susceptance at a bus. Its control system measures bus voltage, compares it to a reference, and adjusts thyristor firing angles to inject or absorb reactive current until voltage returns to the desired level. In voltage control mode, MVAR output is zero at setpoint and increases linearly with deviation.
How does a Bus SVC differ from a STATCOM in industrial applications?
An SVC is a variable-impedance type using thyristor-controlled reactors and capacitors, while a STATCOM is a voltage-source inverter acting like a synchronous generator. STATCOM offers better performance at low voltages, but SVCs are often chosen for large industrial buses due to cost and proven technology.
How is a Bus SVC integrated electrically at a plant?
A high-voltage compensator bus feeds a step-down transformer to a medium-voltage SVC bus, where TCR, fixed capacitors, TSC, and harmonic filters are connected. The SVC control system references the HV bus voltage, and reactive power is injected at MV and reflected to HV via the transformer.
A Bus Static Var Compensator (Bus SVC) is a shunt-connected FACTS device installed on a specific bus in an AC power system. It automatically adjusts thyristor-controlled reactors and capacitors to inject or absorb reactive power, maintaining bus voltage and power factor within prescribed limits. It provides fast-acting reactive power support for voltage stability and power quality.
In manufacturing, Bus SVCs are applied at plant buses (e.g., 13.8 kV or 34.5 kV) to stabilize voltage from fluctuating loads like arc furnaces and rolling mills. They reduce voltage flicker, improve power factor, and prevent nuisance trips of drives and PLCs. The SVC operates in voltage control mode, adjusting reactive power to hold bus voltage near a setpoint, or in fixed MVAR mode. This ensures equipment operates within tolerances, reduces utility penalties, and enhances process reliability on the shop floor.
Mis-coordination of protection and controls at the SVC bus, leading to mis-tripping or failure to trip during faults, violating electrical safety standards.
Harmonic and interference issues from thyristor operation due to undersized or poorly tuned filters, causing overheating and fire risks.
Inadequate worker protection and procedures around high-energy SVC installations, including lack of lockout/tagout and arc-flash labels, violating OSHA and WorkSafeBC requirements.