Testing And Commissioning Guideline For Numerical Distance Protection Relay

Settings for the protection relay

This guideline is entitled “Numerical Distance Protection Relay Commission and Testing” with the aims to calculate appropriate settings for the protection relay, configure the relay, install, commission and testing the entire protection.

Any kind of power system shunt fault results in customers being disconnected if not cleared quickly. Distance protection meets the requirements of speed and reliability needed to protect electric circuits, thus distance protection is used to a large extend on power system networks.

It is a universal short-circuit protection. Its mode of operation is based on the measurement of electrical quantities (current and voltage) and evaluation of the impedance towards the fault, which basically is proportional to the distance to the fault.

The objective of this exercise is to test a modern numerical relay for various faults within the distance zones under consideration.

Three zones are set: Zone one is an under-reaching instantaneous tripping zone set in the forward direction, zone two is an over-reaching zone with single time-delay also set in the forward direction and zone three is an over-reaching zone with double time-delay set in the reverse direction.

Power system model description

The power system model used in this exercise is a three-phase model of a 400 kV transmission, and two loads (two 9 kW three phase resistive loads). The entire model operates at 400 V.

The line model consists of six identical π-sections and each corresponds to 150 km of a 400 kV line. The sections can be connected arbitrarily in series or parallel.

The numerical relay used in this laboratory is the Line distance protection relay REL 511*2.3 from ABB. The REL 511*2.3 is based on a full scheme distance protection function that detects both phase-to-phase and phase-to-earth faults and has a quadrilateral operating characteristics.

A separate general fault criterion with advanced characteristics is used for phase selection and as an overall measuring function, which increases the total operating security and facilitates remote backup applications.

Relay parameters:

• Current: Rated I_r = 1A
  • Nominal range: (0.2 -30) * I_r
  • Operative range: (0.004 – 100) * I_r
  • Permissive overload: 4 * I_r continuous, 100 * I_r for 1 s
• Voltage: Rated U_r = 110V,
  • Nominal range: (80 -120)% of U_r
  • Operative range: (0.001 – 1.5) *U_r
  • Permissive overload: 1.5* U_r continuous, 2.5* U_r for 1 s
  • DC supply for relay: 48 – 250 V.

Figure 1 above shows the line model used for the laboratory.