Simplicity in transformer protection

WHENEVER a fault in a transformer is beginning to form, heat is produced locally, which begins to decompose solid or liquid insulating material and, consequently, to produce inflammable gas. This fact has led to the development of gas-actuated relays for transformer fault protection. Such relays have been in use abroad for many years, and more recently in Canada, but the applications in the United States have been negligible. Small faults develop only slight amounts of gas per time unit. Severe faults, however, quickly develop large amounts of gas and rapidly increase pressure inside the tank. The gas-actuated relays contain two elements: one is a highly sensitive gas-element which operates if gas is developed slowly and which indicates the faults in their incipient stage; the other is a quickly acting pressure element which operates the circuit breakers of the transformer when faults are grave. The experiences have been very good, and the early indications of faults in their incipient stage have reduced greatly the time for, and cost of, repairs. The sensitivity of the gas-actuated relays is considerably greater than that of any type of electrical transformer protection because of the extremely sensitive gas-element which is an important part of the protection. The gas-actuated relay is a simple and economical protective device which also can be applied to special transformers in which electrical methods are complicated, expensive, of very reduced sensitivity, and, therefore, of limited protective value.