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HARMONIC FILTRATION


G5/4 and Levels of Harmonic Distortion

Harmonic distortion can cause severe disturbances to certain electrical equipment and it is the duty of each electrical utility to provide a "clean supply". Many countries, including the United Kingdom, now set legally binding and contractual limits to the harmonic distortion allowable on the distribution networks. In the UK the Electricity Council Engineering Recommendation G5/4 provides for the levels of acceptance for the connection of harmonic generating equipment, defined in the following stages.


STAGE 1

Permits the connection of individual loads up to 14KVA at 415 Volts and 250KVA at 11KV without special consideration. Please view table below for Illustration


Harmonic

2

3

4

5

6

7

8

9

10

6.6, 11 or 20Kv

4.9A

6.6A

1.6A

3.9A

0.6A

7.4A

0.9A

1.8A

1.4A

415v

28.9A

48.1A

9.0A

28.9A

3.0A

41.2A

7.2A

9.6A

5.8A


Harmonic

11

12

13

14

15

16

17

18

19

6.6, 11 or 20Kv

6.3A

0.2A

5.3A

0.5A

0.3A

0.4A

3.3A

0.2A

2.2A

415v

39.4A

1.2A

27.8A

2.1A

1.4A

1.8A

13.6A

0.8A

9.1A


STAGE 2

System Voltage
at the PCC

Stage 2
THD
Voltage Limit

Stage 2
5th Harominc
Voltage Limit

400V

5%

4%

6.6, 11 and 20Kv

4%

3%

22Kv

3%

2%


TABLE OF HARMONIC CONTENT

Order of Harmonic

6 Pulse %

12 Pulse %

1st Fundamental

100

100

5th Fundamental

20

 

7th Fundamental

14

 

11th Fundamental

9

9

13th Fundamental

8

8

17th Fundamental

6

 

19th Fundamental

5

 

23rd Fundamental

4

4

35th Fundamental

4

4


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