3.2　Current Measurement

3.2.1　The AC current of the following circuits shall be measured:

1　Stator circuits of synchronous generators and generator/motors.

2　One side of two-winding main transformers，three sides of three-winding main transformers，three sides of auto-transformers and the common winding circuits of auto-transformers.

3　One side and individual branch circuits of double-winding auxiliary transformers，three sides of three-winding auxiliary transformers and HV side of excitation transformers of generators.

4　Incoming line circuits of a diesel generator that are wired to the incoming lines of LV emergency busbar sections and AC UPS.

5　The power lines at 1200V and above and trunk lines for power supply，distribution network and electricity consumption network at a voltage level below 1200V.

6　Circuits of the breakers adopting 3/2，4/3 and angle-type wiring schemes respectively at a voltage level of 220kV and above.

7　Circuits of busbar tie breakers，busbar sectionlizing breakers，bypass breakers and bridge circuit breakers.

8　Shunt reactor bank together with its neutral small reactance at a voltage level of 330kV and above，and circuits of shunt reactors and shunt capacitors at 10-66kV.

9　Circuits of lighting transformers and arc suppressing coils at 50kVA and above.

10　Motors of 55kW and above and emergency motors of below 55kW.

3.2.2　In addition to the requirements as specified in 3.2.1 of this Code，the three-phase AC current shall be measured for the following circuits:

1　Stator circuits of synchronous generators and generators/motors.

2　Transmission lines and transformer circuits at 110kV and above.

3　Main circuits of the shunt reactor banks at 330kV and above and the transformers with reactive compensators installed at LV sides.

4　Lighting transformers，transformers used for both lighting and power system，and power lines at a voltage level below 3kV feeding both lighting and power system with lighting loads accounting for 15% and above of the total load.

5　Power consumer lines at 1200V and above with a three-phase load unbalance of more than 10%，and power supply lines at a voltage level below 1200V with a three-phase load unbalance rate of more than 15%.

3.2.3　The following circuits should have the negative sequence current measured.And the measuring instruments used shall have an accuracy class not lower than class 1.0.

1　Large-capacity steam turbine-generators with the negative sequence current overload capacity being less than 10.

2　Generators with the load unbalance being larger than 10% of rated current.

3　Lines at 1200V and above with the load unbalance being larger than 0.1 times the rated current.

3.2.4　DC current shall be measured for the following circuits:

1　Excitation circuits of synchronous generators，generator/motors and synchronous motors as well as output circuits of automatic and manual excitation adjustment system.

2　DC generators and their excitation circuits as well as DC motors and their excitation circuits.

3　Output circuits of battery packs as well as output circuits of charging and float charging rectifying devices.

4　DC output circuits of major power rectifying devices.

3.2.5　Current measurement of rectifying devices should involve harmonic monitoring.