A load containing harmonie generatng equipment is connected through a step-down

Question

A load containing harmonie generatng equipment is connected through a step-down transformer to a 12.47 kV utility distribution feeder. A 5th harmonic filter has been added to the plant bus to filter out the majority of the 5th harmonic current.The PCC is considered to be the 12.47 kV connection to the step-down transformer. The short circuit capacity at the PCC is 55 MVA at 12.47 kV. The maximum fundamental load current is 40A at 12,47 kV The following harmonic currents are present on the utility svstem as a result of this load: Harmonic Order Current (Amps) 2.5 3.8 Frequency 300 420 660 780 1020 13 17 0.6 0.4 Determine whether the load is in compliance with IEEE Standard 519.

Explanation / Answer

The voltage at point of common coupling (PCC) is 12.,47 KV

Short circuit capacity at PCC is 55 MVA

Maximum short circuit current at PCC is Isc = 55 /(1.732 * 12.47) = 2.55 KA

The maximum fundamental load current (IL) = 40 A

5th harmonic current distortion as percentage of IL = 2.5*100/40 = 6.25

7th harmonic current distortion as percentage of IL = 3.8*100/40 = 9.5

11th harmonic current distortion as percentage of IL = 1.6*100/40 = 4

13th harmonic current distortion as percentage of IL = 0.6*100/40 = 1.5

17th harmonic current distortion as percentage of IL = 0.4*100/40 = 1

The total demand distortion (TDD) is equal to the square root of the sum of squares of each of the maximum demand harmonic currents as percentage of IL(divided by the maximum demand load current at the fundamental) = 12.188

Isc / IL= 63.66; As per the IEEE Standard 519-2014,at this ratio

the maximum allowed harmonic current distortions for harmonics in between 3 to 7 at PCC of 12.47 KV is 10 and in between 11 to 17 is 4.5 and The total demand distortion (TDD) allowed is 12 at 12.47KV.

So, As per the above calculations ,The load is not able to meet TDD < 12 .The current harmonics at PCC made the load not in compliance with IEEE Standard 519.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.