Saudi Electricity Company Technical Standards and Guidelines

SLIDE 1 – What Is the Standard Medium Voltage Level Used by SEC?

Answer:
The standard Medium Voltage (MV) level used by the Saudi Electricity Company (SEC) is 13.8 kV. This is the mandatory distribution voltage for most commercial and industrial projects. All MV switchgear, transformers, and protection systems must be rated accordingly.

SLIDE 2 – What Is the Standard System Frequency in SEC Networks?

Answer:
The official SEC system frequency is 60 Hz. Any equipment rated at 50 Hz is not accepted. All generators, motors, transformers, and protection relays must be designed for 60 Hz operation.

SLIDE 3 – What Earthing System Is Required by SEC?

Answer:
SEC requires the TN-S earthing system, where:
• Neutral and earth are separated from the source
• Protective earth (PE) is independent
This ensures higher safety, reduced fault risk, and better protection performance.

SLIDE 4 – What Is the Maximum Allowable Voltage Drop According to SEC?

Answer:
The maximum permitted voltage drop is 5% from the source to the final load.
Simple check formula:
Voltage Drop (%) = (√3 × I × L × R) / V × 100
Exceeding 5% leads to rejection during SEC design review.

SLIDE 5 – What Are the Approved Cable Types and Installation Requirements?

Answer:
SEC mandates:
• XLPE insulated power cables
• Minimum burial depth for underground cables
• Mechanical protection using concrete tiles or protective ducts
Improper burial depth or wrong insulation type is a common rejection reason.

SLIDE 6 – What Transformer Vector Group Is Mandatory in SEC Projects?

Answer:
The required vector group is Dyn11.
This provides:
• Proper phase displacement
• Stable LV system operation
• Compatibility with SEC protection philosophy
Any other vector group requires special written approval.

SLIDE 7 – What Short-Circuit Rating Is Required for SEC Equipment?

Answer:
Typical SEC short-circuit rating requirements range between 50 kA to 80 kA, depending on:
• Network location
• Fault level
• Substation type
All switchgear must be designed to safely withstand these fault currents.

SLIDE 8 – What Current Transformer (CT) Accuracy Classes Are Required?

Answer:
SEC requires specific CT accuracy classes for:
• Metering CTs (high accuracy for billing)
• Protection CTs (high accuracy during faults)
Wrong CT class causes wrong protection operation or billing errors.

SLIDE 9 – What Are the Main Cable Installation Rejection Points by SEC?

Answer:
Most common rejection reasons are:
• Insufficient burial depth
• Incorrect cable spacing
• Poor trench bedding
• Lack of mechanical protection
SEC inspections focus heavily on underground cabling quality.

SLIDE 10 – Why Do Many Electrical Projects Fail SEC Approval?

Answer:
Projects usually fail due to:
• Incorrect earthing (non-TN-S)
• Under-rated short-circuit levels
• Wrong transformer vector group
• Excessive voltage drop
• Incorrect CT accuracy class
SEC approval is compliance-based, not negotiation-based.

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