Protection requirements for a multi-terminal meshed DC grid

• Multi-terminal high voltage direct current (HVDC) or meshed DC grid is considered to be the preferable option for the much anticipated future supergrid for Europe. This supergrid should connect distant generators to increase the introduction of renewable energy sources and to provide an increased security to the pan- European power system. Although many technical limitations remain, the protection system is often regarded as the most critical one. The protection system for a meshed DC system has particular difficulties compared to the traditional AC system because of the DC current that has no zero crossings and the line impedance that does not limit the fault current. As a consequence, the DC currents will rise much faster and interrupting the fault current is significantly more difficult in the meshed DC than it is in an AC meshed system. Furthermore, traditional protection devices such as impedance relays cannot be used. New alternatives must be found, such as considering a joint strategy between the protection devices and the VSC converter controls. In order to provide a reliable supply of electric energy, the protection system of a meshed DC system should have a number of minimum requirements: fast fault detection, selectivity in opening the correct breakers, and redundancy.This paper discusses the different requirements for the protection of a multi-terminal meshed HVDC system. It will provide a list of boundary conditions for such a protection system, as well as an overview of the current state of the technology and the remaining gaps. Some pointers to potential technologies that may be used in the future grid protection are given. The paper will not focus on hardware developments, but will rather indicate the requirements that these devices (or joint set of devices) must fulfill.

Subject headings

TEKNIK OCH TEKNOLOGIER  -- Elektroteknik och elektronik -- Annan elektroteknik och elektronik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Electrical Engineering, Electronic Engineering, Information Engineering -- Other Electrical Engineering, Electronic Engineering, Information Engineering (hsv//eng)

Keyword

Multi-terminal

Protection system

Selectivity in meshed grids

VSC HVDC

Publication and Content Type

ref (subject category)

kon (subject category)