ΕΓΓΡΑΦΕΙΤΕ ΣΤΟ ΚΑΝΑΛΙ ΜΑΣ ...

EN50160:2010 Report

Summary

The EN50160:2010 Report shows an analysis of the compliance of selected sources based on the EN50160:2010 power quality standard.

Use this report for an analysis and compliance assessment of your facility against the EN50160: 2010 power quality standard.

Details

EN50160: 2010 is a set of power quality standards used by certain energy suppliers and energy consumers.

The EN50160: 2010 report uses the following measurements of the supply voltage:

Supply voltage dips
Temporary overvoltage
Supply voltage unbalance
Harmonic voltage
Interharmonic voltage
Power Frequency
Voltage magnitude
Rapid voltage changes (and Flicker)
Short- and
long-term interruptions

Use the EN50160: 2010 report template to create a report containing comprehensive analysis of all EN50160: 2010 compliance data logged by multiple meters.

The compliance summary is based on the EN50160: 2010 limits for each observation period: each default EN50160 measurement indicates a pass or did not pass on the compliance test with a Y (yes) or N (no) respectively.

VIDEO ON POWER ADVISOR

Unbalanced voltage causes

All electrical networks suffer from power quality issues in varying degrees and frequencies.

Brief sags and surges are common but networks can exhibit voltage supply irregularities that may be present for prolonged periods of time, or are constantly present on the network. Where a voltage imbalance exists on a supply network, it is usually due to generation faults, unmatched impedance on transformer banks, or large single phase loads on the three phase network.

Customer installation produced voltage imbalances are most commonly the result of single phase loads not connected evenly across the 3 phase system. Single phase motors, heating and cooling loads are very commonly connected in such a manner that one phase conductor carries significantly more current than the other two.

The Line to Neutral Voltage of one phase is lower than the other two.

Similarly, where the majority of the load is connected over only two phases, one Line to Neutral voltage is higher than the other two. In either case, Line to Line voltages are affected.

Figure 1 demonstrates an over voltage on one line, and an under voltage on another at the Medium Voltage (MV) or High Voltage (HV) transformer, while the third is at specified voltage.

On the Low Voltage (LV) secondary, not only are the Line to Neutral voltages on two phases clearly over and under by 10% respectively, measuring the Line to Line vectors (dashed lines) shows voltage varying from specification.

Further reading is available in other papers referencing phase angle shift that occurs with unbalanced voltage in three phase installations.

Unbalanced voltage and induction motors

The effect of unbalanced voltage on induction motors is widely known by most technicians and plant engineers.

Motor torque and speed are negatively affected and the motor may produce excessive noise.

The voltage imbalance can also cause an increase in current imbalance and a temperature rise far greater than the voltage imbalance percentage.

We can calculate the increased temperature in an induction motor winding as a result of voltage imbalance.

Voltage imbalance in a 3 phase system is expressed as a single percentage.

As in Figure 1, there may exist an under voltage and an over voltage.

To calculate the system imbalance and the resulting temperature rise in the winding, the following formulae are used:

The table in Figure 2 demonstrates the formula above outlining the exponential winding temperature increase compared with the increase in voltage imbalance.

An imbalance greater than 2% is unacceptable, as it results in a temperature rise in the winding that will be beyond the motors specification; the life of the motor may be decreased. NEMA limits require no more than 5% unbalanced voltage.

Studies show that the usefull life of the motor halves (!) with every 10% of the mormal insulating material working temperature increase.

Three phase induction motors should be de-rated according to the chart below.

Not only does the increased operating heat induce premature expiration of the motor, excess current is also drawn with no additional power output, therefore over-stressing the supply cables and potentially reaching levels where the current overloads and the Variable Speed Drives (VSD) over current protection will trip.

VSD diodes, DC link capacitors and rectifier power supplies will experience additional thermal stress as a result of the increased AC line currents-to compensate for the voltage imbalance.

Triple harmonics can also be produced as a result of the increased stress to the rectifier diodes.