Gas pressure and temp. monitor and switchgear - has temp. related pressure characteristic held in ROM for comparison

摘要

The gas pressure/temperature monitor for gas-quenched electrical switchgear consists of a temperature sensor (1) which monitors the temperature of the quenching medium, e.g. Sulphur Hexachloride. The signal is converted to digital form (5) as an address for a read-only-memory (6) in which is stored the density characteristic for the gas. The temperature-related pressure is compared with the actual value of the gas pressure as sensed by a pressure gauge (7). This signal is digitised and fed to an 8-bit comparator (10). If the actual value falls below the desired value, then a relay is energised (11) to operate an alrm. In order to provide an additional signal when the acutal value approaches a critical value, a second comparator is used (12) which is fed from the ROM via an adder (13) whose second input is fed with an additional set point value.