Why Did AC220V Drop to AC80V? Electric Ball Valve Failure Caused by 600-Meter Line Voltage Drop

In industrial automation control systems, the reliable operation of electric ball valves is critical to process safety and efficiency. The following case study outlines a recent troubleshooting example where an electric ball valve installed on an industrial park gas pipeline failed to open or close after wiring completion. Through systematic inspection and professional analysis, our team quickly identified the root cause and implemented an effective solution. We share the process below for industry reference.

Technical Specifications

• Application Scenario: Industrial park gas pipeline
• Purpose: Main gas pipeline shut-off
• Medium: Natural gas
• Valve Size: DN300
• Body Material: WCB
• Connection Type: Flanged
• Control Signal: Switch signal
• Operating Power Supply: AC220V
• Design Life: 6 years
• Commissioning Date: December 2024
• Installation Location: Shanghai

After completing the cable connection between the electric ball valve and the control cabinet, operators found the valve would not open or close upon command. This failure disabled the gas pipeline’s regulation function, directly impacting the normal gas supply for park enterprises.

Troubleshooting & Analysis

The GRAT technical support team intervened promptly. Initial inspection confirmed correct wiring, followed by systematic measurement of electrical parameters:

• The actual voltage measured at the electric actuator terminals was only AC80V, significantly lower than the rated AC220V.
• According to the power formula P = UI (actuator power is 1.2kW), with constant power, a decrease in voltage leads to an increase in current.
• The measured operating current reached 18A. This excessive current triggered the control cabinet’s built-in over-current protection, preventing the electric ball valve from operating.

Root Cause Analysis:
The severe voltage drop was primarily due to the long cable distance of 600–700 meters between the electric ball valve and the control cabinet. Over such a long distance for power transmission, the significant voltage drop made it impossible to meet the voltage required for normal actuator startup.

Key factors affecting line voltage drop include:

• Conductor material (e.g., copper core cable has lower resistivity and smaller voltage drop)
• Line length (longer length increases voltage drop)
• Conductor cross-sectional area (larger area reduces resistance and voltage drop)
• Ambient temperature (higher temperature increases conductor resistance)

This situation highlights a critical design consideration: preventing excessive voltage drop on electric ball valve installations, especially over long distances.

Solution & Implementation

Addressing the fault root cause, we evaluated two feasible solutions:

1. Change Voltage Rating: Modify the actuator operating voltage from AC220V to AC380V. While AC380V offers stable voltage and lower current, this option was excluded due to the absence of an AC380V power source on site, high costs for actuator replacement, and potential compatibility issues.
2. Relocate Control Cabinet: After discussion with on-site personnel, the control cabinet was moved closer to the ball valve, and wiring was reinstalled. Post-relocation testing confirmed the ball valve resumed normal operation, resolving the fault.

Implementation Results:
After deciding on Solution 2, our construction team executed the plan promptly. The control cabinet was repositioned approximately 50 meters from the electric ball valve. New power and control cables were installed according to specifications. Post-modification debugging and testing included:

• Measuring voltage at the actuator input with a precision voltmeter, confirming a stable AC215V, fully meeting the rated requirement.
• Checking the starting current with a clamp meter, showing a stable reading of 8.2A, within the normal operating range.
• Conducting multiple open/close operation tests, with the electric ball valve responding accurately and reliably to control signals.

After 72 hours of continuous monitoring, all system parameters remained stable, confirming the fault was completely eliminated.This successful resolution not only fixed the immediate problem but also provided valuable insights for planning the layout of electric actuators in similar conditions, serving as a key reference for future project design.

Experience Summary

This case reiterates that during the design and installation phases of industrial automation systems, a comprehensive assessment of electrical system parameters and equipment layout is essential. Particular attention should be paid to:

• Accurately evaluating power supply distances to prevent equipment malfunction due to line voltage drop.
• Scientifically selecting cable specifications, considering larger cross-sectional areas for long-distance power transmission scenarios.
• Ensuring integrated planning considers power matching, equipment placement, and control logic.

Effectively managing the voltage drop on electric ball valve systems is crucial for reliability. GRAT remains committed to providing professional technical services and rigorous fault analysis, delivering reliable control valve solutions to ensure the safety, stability, and efficiency of industrial systems. We welcome inquiries and cooperation from clients across various sectors.