Installation of Submersible Pump Cables

Submersible cables are critical for powering underwater equipment such as pumps, lights, and motors in applications ranging from water wells to industrial underwater operations. Proper installation of these cables ensures efficient performance, longevity, and safety. This article aims to provide electrical engineers with a guide to the installation of submersible cables, focusing on best practices, tools, and safety considerations. Additionally, it will make a case for the use of Nitrile Rubber submersible cables due to their superior properties in underwater environments. It will also provide an example of sizing a cable for a 6.5kW pump.

Understanding Submersible Cables

Submersible cables are specially designed to operate in wet environments. They are constructed with waterproof jackets/insulation to prevent electrical shorts and degradation.

The Case for Nitrile Rubber Submersible Cables

Nitrile Rubber (NBR) cables offer several advantages that make them an excellent choice for submersible applications. Here’s why they stand out:

1. Superior Flexibility and Durability

Nitrile Rubber cables are highly flexible, making them easier to install in tight spaces and around bends without risking damage. Their robust construction resists mechanical stress, which is common in underwater environments.

2. Excellent Chemical Resistance

Nitrile Rubber is known for its exceptional resistance to a wide range of chemicals, oils, and fuels. This property is particularly beneficial in industrial applications where cables may be exposed to hazardous substances.

3. High Water Resistance

NBR cables provide superior water resistance, preventing moisture ingress that can lead to electrical faults. This makes them highly reliable in submersible applications, where continuous exposure to water is inevitable.

4. Temperature Resistance

These cables can withstand a broad temperature range, ensuring consistent performance in varying underwater conditions, from cold deep-water environments to warmer, more temperate waters.

5. Longevity and Cost-Effectiveness

The durability of Nitrile Rubber cables translates to a longer service life and reduced maintenance costs. Investing in these cables can lead to significant savings over time due to fewer replacements and repairs.

Pre-Installation Preparation

1. Site Assessment

- Evaluate the environment: Identify potential hazards, water depth, and quality (freshwater, seawater, or chemically treated water).

- Check regulations: Ensure compliance with local electrical codes and standards (e.g., NEC, IEC).

2. Cable Selection

- Voltage rating: Choose a cable that matches the system’s voltage requirements.

- Insulation and sheathing: Ensure the cable insulation is appropriate for the environmental conditions. Water ingress can mean damage to your pump and pose a safety risk.

- Length and size: Calculate the required cable length, considering the distance and any potential voltage drop.

### Example: Sizing a Cable for a 6.5kW Pump

Let's consider a 6.5kW submersible pump operating at a voltage of 400V, with a distance of 100 meters from the power source. We'll determine the appropriate cable size for this application.

#### Calculations

1. Determine the Current:

- Power (P) = 6.5kW

- Voltage (V) = 400V

- Power Factor (pf) ≈ 0.85 (assuming a typical value for motors)

- Efficiency (η) ≈ 90% or 0.90

2. Voltage Drop Calculation:

- Let's assume a permissible voltage drop of 3%.

3. Select Cable Size:

- Based on standard tables for copper conductors, a cable with a cross-sectional area of 4mm2 has a resistance of approximately 0.0046 Ω/m, for DC applications corrected to 20degC which meets the required resistance.

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#### Conclusion for Cable Size:

- A 4mm2 Nitrile Rubber submersible cable is suitable for this application, considering the calculated current and voltage drop over 100 meters.

Installation Process

1. Cable Handling and Preparation

- Inspect the cable: Check for any physical damage before installation.

- Lay out the cable: Unwind the cable carefully to avoid cuts, kinks and bends.

- Mark the length: Measure and mark the required length, considering additional length for connections and terminations. Reputable manufacturers will have the meter markings printed along the length of the cable.

2. Connection and Termination

- Stripping: Carefully strip the cable ends using appropriate stripping tools. Avoid damaging the conductors. Every one of the many strands counts and contributes to the current carrying capacity of the cable. For the 4mmsq the strands should be at least 56 strands of 0.3mm diameter each.

- Crimping: Use crimping tools to attach connectors or terminals securely. Ensure a firm and corrosion-resistant connection. I liked this guide by Water Bore Pump

- Waterproofing: Apply heat shrink tubing or waterproof tape to seal connections. For added protection, consider using waterproof connectors designed for submersible applications.

3. Cable Placement

- Routing: Place the cable along the predetermined path, avoiding sharp bends and abrasive surfaces.

- Securing: Use cable ties or clamps to secure the cable at regular intervals. Ensure the cable is not under tension.

- Protection: If necessary, use conduit or protective covers to shield the cable from physical damage and environmental factors.

4. Testing and Commissioning

- Continuity testing: Verify the electrical continuity of the cable to ensure there are no breaks or shorts.

- Insulation resistance testing: Use a megohmmeter to check the insulation resistance, ensuring it meets the required specifications. General rule is at minimum 1MΩ.

- Operational testing: Power up the system and monitor the performance of the submersible equipment. Look for any signs of electrical issues or leakage.

Safety Considerations

- Personal protective equipment (PPE): Always wear appropriate PPE, including gloves, safety glasses, and insulated tools.

- Lockout/tagout (LOTO): Follow LOTO procedures to ensure the power supply is disconnected during installation.

- Moisture management: Keep the work area as dry as possible to prevent accidental electric shocks.

- Training and certification: Ensure all personnel involved in the installation are properly trained and certified for working with submersible cables.

Maintenance and Inspection

Regular maintenance and inspection are crucial for the longevity and reliability of submersible cables. Periodically check for:

- Physical damage: Inspect the cable for cuts, abrasions, or signs of wear.

- Water ingress: Ensure that all joints and terminations remain waterproof.

- Electrical performance: Monitor the system’s electrical performance for any irregularities.

Conclusion

Proper installation of submersible cables is essential for ensuring the safe and efficient operation of underwater electrical systems. Nitrile Rubber submersible cables, with their superior flexibility, chemical resistance, and durability, offer significant advantages over other types of cables, making them a preferred choice for many submersible applications. By following the guidelines outlined in this article and accurately sizing the cable for specific applications like the 6.5kW pump example, electrical engineers can achieve reliable installations that stand the test of time. Regular training and adherence to safety standards will further enhance the effectiveness and safety of submersible cable installations.