UL 977-2012 pdf download

UL 977-2012 pdf download.Fused Power-Circuit Devices.
42+3 Galvanometers shall be calibrated as described in 42.4 — 42.8.
42.4 When a shunt is used to determine the circuit characteristics, a direct-current cahbrating voltage is normally used. The voltage applied to the oscillograph galvanometer circuit is to result in a deflection of the galvanometer approximately equivalent to that which Is expected when the same galvanometer circuit is connected to the shunt and the nominal short-circuit current is flowing. The voltage is to be applied so as to cause the galvanometer to deflect in both directions. Additional calibration is to be made using approximately 50 percent and 150 percent of the voltage used to obtain the deflection indicated above. The sensitivity of the galvanometer circuit in volts per inch (or millimeter) is to be determined from the deflection measured in each case, and the results of the six trials averaged. The peak amperes per inch (or millimeter) is obtained by dividing the sensitivity by the resistance of the shunt. This multiplying factor is used for the determination of the rms current as described in 44.2.1.
42.5 A 60 Hz sine-wave potential may be used for calibrating the galvanometer circuit, using the same general method described in 42.4. The resulting factor must be multiplied by 1,414.
42.6 When a Current transformer is used to determine the Circuit characteristics, an alternating-Current is used to calibrate the galvanometer circuit, The value of current applied to the galvanorneter circuit is to result in a deflection of the gatvanometer approximately equivalent to that which is expected when the same galvanometer is connected to the secondary of the current transformer and nominal short-circuit current is flowing in the primary. Additional calibrations are to be made at approximately 50 percent and 150 percent of the current used to obtain the deflection indicated above. The sensitivity of the galvanometer circuit in amperes rms per inch (or millimeter) is to be determined in each case and the results averaged. The average sensitivity is multiplied by the current-transformer ratio and by 1.414 to obtain peak amperes per inch (millimeter). This constant is used for the determination of the rrns current as described in 44.2.1 –
42.7 All the galvanometer elements employed are to align properly in the oscillograph. or the displacement differences are to be noted and used as needed.
42,8 The sensitivity of the galvanometers and the recording speed is to be sufficient to provide a record from which values of voltage, current, and power factor can be measured accurately. The recording speed is to be not less than 60 inches per second (1.52 m per second), and higher speeds are recommended.
43 Circuit Measurement Verification
43.1 A noninductive (coaxial) shunt that has been found acceptable for use as a reference (coaxial) shunt shall be used to verify the manufacturer’s instrumentation. This may be accomplished by connecting the shunt in series with instrumentation of each phase of the manufacturer’s test circuit. A single-phase circuit of the same voltage and current as that required for the switch test is to be used.
432 The circuit is to be closed as nearly as possible at the angle which will produce a current wave with maximum offset. The short-circuit current and voltage are to be recorded. The primary voltage should be recorded if primary closing is used. The current and power factor measured by the reference shunt should be within 5 percent of that measured using the manufacturer’s instrumentation
43.3 If the reference shunts are aaiIabIe, one can be inserled in each of the ptiase legs and a 3 phase circuit establ.sied at the same voltage and current as the test circuit. Controlled closing is not required for polyphase circuits. The same instrumentation accuracy is applicabfe as stated in 43.2.