Sonel PQM analyzers case study #5: Assessment of compliance with EN 50160

Power Quality (PQ) can be defined according to many criteria. One of them is the EN 50160 standard for public distribution networks. Obtaining reliable and comparable results requires the use of a class A device compliant with the EN 61000-4-30 standard.

Description of the identified problem

The user connected to the LV 230 V AC distribution network wants to know the power quality at the connection point. Frequent flickering phenomena disturb him greatly. What can be said about the phenomena occurring? Is it possible to justify what is the cause of the observed condition?

Measuring equipment used

• Sonel PQM-702 Power Quality Analyzer (see the product successor Sonel PQM-710)
• Set of F-1A current probes (4 x 3000 A AC, 3 turns)
• Sonel Analysis software

Fig. 1. EN50160 report - header and graphical summary of the results

 

Fig. 2. Statistics f, U, Plt - are they within the tolerance during 95% of the observation time and what values do they not exceed?

 

Fig. 3. Statistics of voltage unbalance and harmonics

 

Fig. 4. Voltage harmonic statistics - levels during 95% of the observation time

 

Fig. 5. Statistics of events and multiphase events

 

Fig. 6. Statistics of rapid voltage changes (RVC)

 

Initial conclusions (Fig. 1. to 6.)

1. Assess the properties of the collected data in General information part:

a) the measurement period of 1 week requirement is fulfilled,

b) the quantity of accumulated averaging periods is sufficient,

c) the registration criteria are adapted to the measured network.

2. The graphical presentation marked in red indicates the deviations found.
3. Statistics of voltage tolerance exceeding:

a) in L2 phase - the voltage was lower than 253 V for less than 45% of the time,

b) in all phases the tolerance of 253 V was exceeded, however in L2 for almost 70% of the observation time.

4. The Plt flicker coefficient statistics were as follows:

a) exceeded in phase L3 all the time (Plt was greater than 1),

b) within the tolerance in L1 for 31% of the time and in L2 for 18% of the observation time,

c) During 95% of the observation time, it was not greater than 3.3 in L1, 3.5 in L2, and 2.7 in L3.

5. Unbalance did not meet the condition of tolerance in 48.8% of the observation time, not exceeding 3.6% during 95% of the observation time.
6. The voltage harmonics were within the tolerance during 95% of the time, except:

a) Uh15 during 69.44% of observation time was above the 0.5% threshold, not exceeding 0.77% in 95% of the time,

b) Uh21 during 94,18% of observation time was above 0,5% threshold, not exceeding 0,52% in 95% of the time.

7. A very large number of events was found:

a) voltage swells (Un + 10% threshold) reaching values of up to 270.34 V, the longest even over 513.84 seconds,

b) voltage dips (Un - 10% threshold) up to the levels of 134.66 V, the longest lasting 20 690.63 seconds.

8. Multiphase events fell within the tolerance ranges of +20% and -30%.
9. Rapid voltage changes (RVC) occurred daily in very large amounts, especially in phases L1 and L3.
10. The power quality at the measuring point is very low.

 

Fig. 7. Variation of phase and interphase voltages during the observation period

 

Fig. 8. Variation of symmetrical components of three-phase voltage during the observation period

Conclusions:

1. There are very frequent exceedances of the voltage tolerance (Fig. 7), unbalance (Fig. 8) and flicker coefficients Plt.
2. Voltage harmonics exceedances concern only the zero sequence harmonic.
3. The registered parameters of the standard concern only voltages and do not allow for the identification of the causes of the exceedances.
4. The multitude of tolerance exceeding events indicates the possibility of the power line damage.

Recommendations:

1. Urgently notify your energy supplier about very poor power quality.

 

Author:
Krzysztof Lorek