Selection of Surge Protective Device (SPD)- (Part 4)
August 2, 2015 6 Comments
Typical System Voltage & MCOV rating (As per IEEE):
| Typical IEEE System Voltages | |||
| Normal (Line to Line) Voltage (KV rms) | Maximum ( Line to Line ) Voltage (KV rms) | Maximum (Line to Ground) Voltage (KV rms) | Min MCOV |
| kV rms | kV rms | kV rms | kV rms |
| 2.40 | 2.52 | 1.46 | 1.46 |
| 4.16 | 4.37 | 2.52 | 2.52 |
| 4.80 | 5.04 | 2.91 | 2.91 |
| 6.90 | 7.25 | 4.19 | 4.19 |
| 8.32 | 8.74 | 5.05 | 5.05 |
| 12.0 | 12.6 | 7.28 | 7.28 |
| 12.5 | 13.1 | 7.57 | 7.57 |
| 13.2 | 13.9 | 8.01 | 8.01 |
| 13.8 | 14.5 | 8.38 | 8.38 |
| 20.8 | 21.8 | 12.6 | 12.6 |
| 22.9 | 24.0 | 13.9 | 13.9 |
| 23.0 | 24.2 | 14.0 | 14.0 |
| 24.9 | 26.2 | 15.1 | 15.1 |
| 27.6 | 29.0 | 16.8 | 16.8 |
| 34.5 | 36.2 | 20.9 | 20.9 |
| 46.0 | 48.3 | 27.9 | 27.9 |
| 69.0 | 72.5 | 41.9 | 41.9 |
| 115.0 | 121 | 69.8 | 69.8 |
| 138.0 | 145 | 83.8 | 83.8 |
| 161.0 | 169 | 98 | 97.7 |
| 230.0 | 242 | 140 | 140 |
| 345.0 | 362 | 209 | 209 |
| 500.0 | 525 | 303 | 303 |
| 765.0 | 800 | 462 | 462 |
Typical System Voltage & MCOV rating (As per IEC):
| Typical IEC System Voltages | |||
| Normal (Line to Line) Voltage (KV rms) | Maximum ( Line to Line ) Voltage (KV rms) | Maximum (Line to Ground) Voltage (KV rms) | Minimum Uc |
| kV rms | kV rms | kV rms | kV rms |
| 3.3 | 3.7 | 2.1 | 2.1 |
| 6.6 | 7.3 | 4.2 | 4.2 |
| 10.0 | 11.5 | 6.6 | 6.6 |
| 11.0 | 12.0 | 6.9 | 6.9 |
| 16.4 | 18.0 | 10.4 | 10.4 |
| 22.0 | 24.0 | 13.9 | 13.9 |
| 33.0 | 36.3 | 21.0 | 21.0 |
| 47.0 | 52 | 30.1 | 30.1 |
| 66.0 | 72 | 41.6 | 41.6 |
| 91.0 | 100 | 57.8 | 57.8 |
| 110.0 | 123 | 71.1 | 71.1 |
| 132.0 | 145 | 83.8 | 83.8 |
| 155.0 | 170 | 98.3 | 98.3 |
| 220.0 | 245 | 142 | 142 |
| 275.0 | 300 | 173 | 173 |
| 330.0 | 362 | 209 | 209 |
| 400.0 | 420 | 243 | 243 |
SPD and Fuse / CB co-ordination chart:
| Fuse/CB co-ordination chart | |||
| Incoming feeder fuse rating (A) | Incoming feeder CB Rating (A) | SPD fuse rating (A) | SPD CB rating (A) |
| 16 | 6 | 10 | 4 |
| 25 | 10 | 16 | 6 |
| 32 | 16 | 20 | 10 |
| 40 | 20 | 25 | 16 |
| 63 | 32 | 40 | 20 |
| 80 | 40 | 50 | 25 |
| 125 | 63 | 80 | 40 |
| 160 | 80 | 100 | 50 |
| 250 | 125 | 160 | 80 |
| 500 | 250 | 320 | 160 |
Sample Specifications of SPD for 277/480V Supply System
- Voltage :277/480V 3Ø WYE, 480V 3Ø Delta
- Frequency: 50/60Hz
- Surge Technology: 40mm MOV
- Nominal Discharge Rating (IN):20kA
- Maximum Continuous Operating Voltage (MCOV): 320V
- L-L=640V
- L-N=320A
- L-G=320A
- G-N=320A
- Maximum Surge Current, Per Mode (Per Phase) : 200kA (400kA
- Voltage Protection Rating (VPR) (Clamping) : 800V(L-N)/700V(L-L)
- Short Circuit Current Rating (SCCR): 10kA
- Connection Type: Parallel Connection
Reason for Failure of SPD :
Most SPDs will last for many years. The things that cause sudden failure are
- External supply faults such as overvoltage -faulty transformer, MV lines
- Local supply faults -broken or ungrounded neutral.
- Wrongly-selected SPD voltage.
- A surge in excess of the SPD’s rating.
Classes’ of surge arrestors according to impulse current:
1 = Test impulse current for lightning current arresters
2 = Test impulse current for surge arresters
- There are 3 x main categories of lightning surge arresters.
- Class 1/A – (10/350) lightning current arresters, which can withstand direct lightning
- Class 2/B – (8/20) surge arresters, to protect against induced surge currents
- Class 3/C – (8/20) surge arresters, to protect against induced surge currents
Meaning of 20kA (8/20μS) impulse current.
- In 8/20μ The first value (8) is the rise time (from 10% to 90% of peak). The second value (20) is the duration for the test transient to decrease to half its peak value.
Standard for SPD:
- Underwriter laboratories—UL 1449 (3rd Edition 2009)
- IEEE C62.45 (2002)
- NECT National Electrical Code Articles 245, 680 and 800.
- NFPAT 780 Lightning protection code recommendations for the use of surge protection devices at a facility service entrance.
JIGNESH PARMAR
I LIKE IT . IT IS USEFUL FOR ME. THANK Q
Dear Jignesh,I am regularly reading your articles / mail . I passed out electrical engineering in the year 1992. Since then due to some reasons I was not worked in the field which I studied. At present I am in the business of Turnkey Interior project contracting. As I always wish to do some thing concrete in the field of electricals , but confused . Also realizing that I forget the basics . Hence please guide me from where to start . REGARDS
NITIN PATIL NIDHEE ENTERPRISES 9823034624
Dear Sir,
It’s really informative, and very simple presentation to understand a common man.
Thanks a lot…
Sudheesh
Sir, I have a utility pole near my home from which the service(single phase supply 230v) is taken and my distribution box is 20 ft away from the service panel. Kindly suggest me where to install the type 2 spd in the main service panel or in the db box? Since all the sockets in the home are earthed to the earth pit do I need to provide separate earth pit for spd or can I connect it to the existing earth pit. Thank u
Nice attempt Mr. Parmar
However the standards used in India are IEC standards like most of the countries of the world . BIS has also followed the same and published IS/IEC 62305 (all four parts). Kindly update your list accordingly.
Dear sir, its so helpful thank you so much