Measuring the quality of electrical energy

Input data

– Transformation: 20/0,42 kV
– Short-circuit power at 20 kV bus bars at junction point in TS Sk“ = 500 MVA
– The reactive power compensation device has built-in filters [p= 7%]
– Transformer power: 4 × 1600 kVA separately
– Short-circuit voltage: uk* = 6% /.

Measuring instrument used:
FLUKE 435, accuracy class A

Example of measured results

Collected data make overview of the normal load on the TR1 transformer.
Measuring was carried out for 7 days while the reactive power compensation devices were switched off.

Measuring was done on the bus bars 0.42 kV of the transformer terminal 1600 kVA to the main NN board. More important parameters are shown from which all the dynamics in the load change and its consequences in the system are visible. Diagrams give us the complete picture of actions during the operation of loads: state of transformer, voltage, voltage distortion, power distortion as well as the content of higher harmonic components in the grid.

Note: Due to the volume of the report on the quality measuring of electrical energy not all parameters and charts are shown but only specific examples.

1. Display of effective values of phase voltages on – TR1:

Effective maximum values of phase voltages – TR1:

2. Effective values of current display – TR1:

Maximum effective values of current – TR1:

3. Display of effective power values (P, Q, S, cosf) TR1:

1. Active power P – TR1:

a) Mean values – Psr:

b) Maximum values – Pmax:

2. Reactive power Q – TR1:

a) Mean values – Qsr –TR1:

b) Maximum values – Qmax –TR1:

3. Apparent power S –TR1:

a) Mean values – Ssr – TR1:

b) Maximum values – Smax – TR1:

4. Power factor –TR1:

a) Power factor cosφ – TR1:

Voltage asymmetry – T:

Current asymmetry – T:

Voltage fluctuations (flicker)

1. Short-term flicker Pst – T1:

2. Long-term flicker Plt –T1:

Diagram of the fifth current harmonic in TR1:

Diagram of the fifth voltage harmonic in TR1:


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