High-voltage interface relay

A common design principle of these devices is a special galvanic isolation module between the input (control) and the output (switching) circuits of the relay.

Rather, it seems more appropriate to categorize them as a separate class of electrical relays and classify according to characteristics of the galvanic decoupling unit[1][4] by insulation voltage level: by construction of galvanic isolation module: by operational (execution) speed: Although such classification may seem arbitrary, it fully reflects the most important properties of interface relays that have a critical effect on the functions performed by them.

[1] Moreover, the optical fibers themselves are subject to a severe negative effect of ionizing radiation and external mechanical impacts (which is critically important in military applications).

The arrangement of input and output circuits of such systems needs to be widely spaced (requiring a lengthy optical fiber), which drives up the overall dimensions of interface unit.

Another important advantage of gerkotrones is the possibility of their installation directly on HV buses, which minimizes the dimensions of a protection system (unlike the aforementioned opto-electronic interfaces that require lengthy optical fibers).

Opto-electronic interface relay. The HV insulator provides decoupling of circuits under different potentials.
A 75 kV reed switch based interface relay (gerkotrone) 1 – HV part of main insulator formed as dielectric glass; 2 – flange; 3 – main separation part between HV and LV; 4 – LV part of main insulator; 5, 6 – internal and external thread; 7 – control winding; 8 – ferromagnetic core; 9 – reed switch; 10 – capsule for reed switch rotation; 11 – conducting coating of external surface of capsule 10 and internal surface of LV part of main insulator 4; 12 – LV bushing; 13 – reed switch mounting plate; 14 – HV bushing; 15 – reed switch position fixation element; 16 – dielectric nut; 17 – lower layer of epoxy compound with cooper powder (60-70%); 18 – dielectric epoxy resin.