Q&A for SEC Approval

Q&A for SEC Approval

1. What is the standard LV voltage in SEC networks?

SEC uses 400/230 V, 3-phase, 4-wire TN-S system. Neutral and earth must remain separated after the service entrance.

2. What is the standard MV voltage in KSA under SEC?

13.8 kV is the main distribution level. Some regions also use 33 kV, but SEC acceptance focuses on 13.8 kV.

3. What frequency does SEC operate on?

60 Hz only. All equipment must be rated 60 Hz; 50 Hz equipment is not allowed.

4. What earthing system does SEC follow for LV customers?

TN-S system: separate neutral (N) and protective earth (PE), no mixing allowed after the main panel.

5. What is the maximum allowable voltage drop?

3% for feeders, 5% total to the farthest load. SEC checks cable sizing based on this.

6. What minimum insulation resistance is required?

LV cables: ≥ 1 MΩ (tested at 500–1000V)

MV cables: ≥ 5 MΩ (tested at 5 kV)

7. What is the minimum burial depth for LV cables?

0.80 m, plus warning tape at 300 mm above the cable.

8. What is the minimum burial depth for MV cables?

1.10 m, with sand bedding and red warning tape above.

9. What spacing must be maintained between MV and telecom ducts?

Minimum 0.30 m separation horizontally or vertically.

10. What is the minimum bending radius for MV XLPE cables?

Single core: 12 × D

Multi core: 15 × D

11. What cable types are approved for LV feeders?

XLPE insulated, armored (LSF) cables, Cu

12. What cable type is approved for MV feeders?

XLPE insulated, copper or aluminum, screened 12/20 kV, per IEC 60502-2.

13. What short-circuit rating is required for LV panels?

Minimum 65 kA / 1 sec for main LV switchgear unless project demands higher.

14. What CT accuracy class is required for metering?

0.2s or 0.5s for revenue-grade accuracy.

15. What CT accuracy class is used for protection?

5P10 or 5P20, depending on fault level and relay type.

16. What is the required CT polarity?

P1 → Source and P2 → Load. Wrong direction results in negative energy.

17. What is the allowed maximum CT burden?

Typically 5–10 VA for metering. Higher burden causes reading errors.

18. What is SEC’s requirement for meter height?

Meter must be installed between 1.4 to 1.7 m above floor level.

19. Are dual feeders mandatory for major loads?

Yes, main + standby feeders are standard for reliability.

20. What is the required transformer vector group?

Most common: Dyn11, used across SEC distribution networks.

21. What cooling method does SEC specify for distribution transformers?

ONAN, with 65°C temperature rise.

22. What is the standard short-circuit level used for MV network design?

Typically 25 kA at 13.8 kV.

23. Which standard applies to MV switchgear?

IEC 62271-200, metal-clad, internal arc classified.

24. Which protection relays are accepted by SEC?

Relays supporting IEC 61850—like ABB, SEL, Siemens, Schneider.

25. What tests are required for MV cable commissioning?

IR, VLF test, continuity, sheath test, phase identification.