34 Pa. Code § 39.370
Secondaries of current transformers to meters or other devices, should not be opened when alive, until a jumper has been connected across the point of opening or such secondary has been short circuited elsewhere. Before working on arc lights or similar devices, connected to series circuits they shall be short circuited, or, when necessary to avoid hazard, disconnected entirely from such circuits by absolute cut-outs.
34 Pa. Code § 39.370
This section cited in 34 Pa. Code § 39.361 (relating to definitions); 34 Pa. Code § 39.411 (relating to general provisions); 34 Pa. Code § 39.421 (relating to general provisions); 34 Pa. Code § 39.431 (relating to general provisions); 34 Pa. Code § 39.441 (relating to general provisions); 34 Pa. Code § 39.451 (relating to general provisions); 34 Pa. Code § 39.461 (relating to general requirements); 34 Pa. Code § 39.471 (relating to general requirements); 34 Pa. Code § 39.491 (relating to general requirements); and 34 Pa. Code § 39.496 (relating to stringing wires).