3 Terms and Definitions
The terms and definitions specified in GB/T 13498-1992 and those given below apply to this standard:
3.0.1 Continuous rating power
Maximum design power transmitted in an HVDC transmission system from rectifier to inverter under normal operating DC voltage and maximum ambient temperature，with all the cooling equipment available but standby cooling equipment out of service.For a long-distance HVDC transmission system，this means the measured power on the DC line side of DC smoothing reactor at the rectifier.The rating consists of bipolar continuous rating and monopolar continuous rating.
3.0.2 Continuous overload
Maximum allowed continuous transmission capacity by which an HVDC transmission system can operate above its continuous rating power.
3.0.3 2h overload
Power transmission capacity still available for an HVDC transmission system after it continuously operates at any power level ranging from the minimum power to continuous overload，for a duration of 2h.
3.0.4 Temporary overload
Power transmission capacity still available for an HVDC transmission system after it operates at any power level ranging from minimum power to 2h overload value，usually for a duration of 3s，5s，or 10s.
3.0.5 Reduced voltage operation
Continuous operation of an HVDC transmission system at a voltage below normal value due to operating environment and other factors.
3.0.6 （Reactive power）Sub-bank
Smallest switchable AC filter bank，shunt capacitor bank or shunt reactor bank which contains circuit breaker.
3.0.7 （Reactive power）Bank
Grouped combination of all AC filters，shunt capacitors and shunt reactors connected to one filter bus.
3.0.8 Binary switching
Simultaneous switching of two filters or（reactive power）sub-banks.
3.0.9 Dynamic voltage change
Percentage change of AC bus fundamental voltage after response of DC control and before response of converter transformer on-load tap changer.
3.0.10 Steady state voltage change
Percentage change of AC bus fundamental voltage before and after response of all controls（including converter transformer on-load tap changer）.
3.0.11 DC biasing current
DC current produced in converter transformer windings due to unbalanced firing angle，power frequency current in DC lines，occurrence of positive sequence 2nd order harmonic voltage，or rise of earth potential in converter station.
3.0.12 Peak value of continuous operating voltage（PCOV）
Highest continuously occurring crest value of voltage including commutation overshoots.
3.0.13 Crest value of continuous operating voltage（CCOV）
Highest continuously occurring crest value of voltage excluding commutation overshoots.
3.0.14 Step response
See the definition of step response in Appendix A.