D9101

The D9101 is a protection relay for low-voltage three-phase networks, which trips when the insulation deteriorates, made by IEMI in Bucharest and designed at the ICE research institute in Bucharest [1].

ICE’s laboratory for electronic instruments for measuring non-electrical quantities designed approved prototypes for many branches of the economy: strain gauge equipment (some configurations were exported to East Germany in 1971–1974 and 1977–1989), vibration meters, dimensional gauges, ultrasonic non-destructive testers, geophysical well-logging equipment and railway equipment [1]. Its designs were made in series at IEMI (27 types) and at the Precision Mechanics Enterprise (5 types), or in ICE’s microproduction workshop (45 types) for small series and one-off models [1].

According to annex III.2.13 it went into production after 1985. It protected low-voltage three-phase networks with an isolated neutral, mainly industrial ones and especially in mines and oil fields, with capacitances of 0.2–2.2 µF and insulation resistances of 100–10 kΩ per phase: it acted on single-phase fault currents of 20–40 mA within at most 0.1 s and on a uniform degradation of the insulation down to 20–2 kΩ per phase, and could break up to 1 A [2].