Direct current distance protection controllers

A DC distance protection controller, for identifying a fault within a protection zone extending between a first terminal with which the protection controller is in use operatively associated and a set point along a DC power transmission conduit lying between the first terminal and a second terminal within a DC electrical power network, the protection controller being programmed to:

• (i) periodically obtain as respective sampled pairs a measured voltage value and a measured current value of the DC power transmission conduit at the first terminal;
• (ii) isolate in respect of each sampled pair, a fault component voltage value from the corresponding measured voltage value and a fault component current value from the corresponding measured current value to define a respective corresponding isolated pair;
• (iii) calculate from each isolated pair of fault component voltage and current values a fault component operating voltage of the DC power transmission conduit at the set point along the DC power transmission conduit;
• (iv) compare a given calculated fault component operating voltage with a historical voltage value derived from a historical measured voltage value from an earlier sampled pair of measured voltage and current values;
• and
• (v) identify a fault within the protection zone when the given calculated fault component operating voltage is greater than the historical voltage value with which it is compared, and
• (vi) identify a distance value from the first terminal to a location associated with the identified fault, based on a relationship between the fault component voltage value and the calculated fault component operating voltage,
• wherein the protection controller includes a phase-mode transformation block configured to calculate the measured voltage value in the form of a positive-mode voltage value based on the positive measured samples and negative measured samples for the DC power transmission conduit, and to calculate the measured current value in the form of a positive-mode current value based on positive current measured samples and negative current measured samples for the DC power transmission conduit.