The objective of this Technical Report is to present the "state of the art" with respect to general guidance on the steady-state performance demands of VSCHVDC transmission systems. It concerns the steady-state performance of two-terminal VSCHVDC transmission systems utilizing converters with power flow capability in both directions.

Different configurations of a VSCHVDC transmission system are covered in this document, including the symmetrical monopolar, asymmetrical monopolar, bipolar with earth return, bipolar with dedicated metallic return and rigid bipolar configurations.

There are many variations between different VSCHVDC transmission systems. This document does not consider these in detail; consequently, it cannot be used directly as a specification for a particular project, but rather to provide the general basis for the system steady-state performance demands.

Normally, the performance specifications are based on a complete system including two VSCHVDC converter stations. However, sometimes a VSCHVDC transmission system can also be separately specified and purchased from multiple vendors instead of single turnkey vendor. In such cases, due consideration can be given to the coordination of each part with the overall VSC HVDC system performance objectives and the interface of each with the system can be clearly defined. The major components of the VSCHVDC transmission system are presented in IEC 62747.

Referring to IEC 62747, an HVDC substation/converter station is defined as that part of the VSCHVDC transmission system which consists of one or more VSC converter units installed in a single location together with buildings, reactors, filters, reactive power supply, control, monitoring, protective, measuring and auxiliary equipment. The AC substations are not covered in this document.

This document provides guidance and supporting information on the procedure for system design and the technical issues involved in the system design of VSCHVDC transmission projects for both owners and contractors. This document can be used as the basis for drafting a procurement specification and as a guide during project implementation.