Share

TB 078 1994 SC 14 WG 14.01.02 Voltage and current stresses on thyristor valves for static var compensators.

The application of SVC employing thyristor valves in power transmission systems has been rapidly increasing in the past decade. Nevertheless there is no International Standard for testing of the valves. As an essential step in developing a guideline the TF undertook a thorough review of the electric stresses experienced by the thyristor valves in operation.

 Download TB from ecigre website 

TABLE OF CONTENTS

PART I VALVES FOR THYRISTOR CONTROLLED REACTOR  (TCR) TYPE STATIC VAR COMPENSATORS

1. Introduction

2. Basic Configurations

3. Functions of the Valve

      3.1 General

      3.2 Functional Structure of a Valve

            3.2.1 Grading Network

            3.2.2 Valve Reactors

            3.2.3 Firing and Monitoring Systems

            3.2.4 Overvoltage Protection

            3.2.5 Overcurrent Protection

            3.2.6 Thermal Overload protection

4. Stresses under Steady-State Operating Conditions

      4.1 Effect of A.C. System and SVC Components on TCR Valve Stresses

            4.1.1 Impedance of Transformer and A.C. System

            4.1.2 TCR with Fixed Capacitor Banks (FC)

            4.1.3 TCR with Thyristor Switched Capacitor Banks (TSC)

      4.2 Switching Stresses

      4.3 Thermal Stresses

            4.3.1 Thyristor

            4.3.2 Damping Resistors

            4.3.3 Other Components

5. Stresses under Transient Conditions

      5.1 AC System Faults

      5.2 Temporary Overvoltages

      5.3 Switching Surges

      5.4 Fast Surges Transferred from the A.C. System

      5.5 Effect of Insulation Failure on Off-State Valves

      5.6 Effect of Insulation Failure on Conducting Valves

      5.7 Control Malfunction

            5.7.1 False Firing

            5.7.2 Firing Failures

            5.7.3 Control Interaction with Power System

6. Conclusions

7. References

PART II VALVES FOR THYRISTOR SWITCHED CAPACITOR  (ISC) TYPE STATIC VAR COMPENSATORS

1. Introduction

2. Basic Configurations

3. Functions of the Valve

      3.1 General

      3.2 Functional Structure of a Valve

            3.2.1 Grading Network

            3.2.2 Valve Reactors

            3.2.3 Firing System

            3.2.4 Supervision System

            3.2.5 Overvoltage Protection

            3.2.6 Overcurrent and Thermal Protection

4. Stresses under Steady-State Operating Conditions

5. Stresses under Transient Conditions

      5.1 A.C. System Faults

      5.2 Temporary Overvoltages

      5.3 Fast Surges Transferred from the A.C. System

      5.4 Lighting Strikes Directly on the Low Voltage Bus

      5.5 Switching Surges

      5.6 Current Stresses on Conducting Valve as a Result of The Previous Cases 5.3 - 5.5

      5.7 Insulation Failures

            5.7.1 Phase to Earth

            5.7.2 Phase to Phase

      5.8 Control Malfunction

            5.8.1 False Firing

            5.8.2 Loss of Firing Signals

            5.8.3 Misoperation of the Voltage Control Loop

            5.8.4 Loss of Synchronization

      5.9 Transformer Saturation Harmonic Effects

6. Conclusions

7. References