What is the laying spacing between the power cable and the instrument cable for a 380V electric valve? In a superior position
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The electric valve has a power consumption of 250W and operates at 380V; it shares the same aluminum alloy cable tray as the instrument signals (24V control wires and 4–20mA signal wires, all of which go to the DCS), with a partition separating them. Since the electric valve is considered an instrument device, its wiring was designed by the instrumentation team. The owner claims that it does not comply with the standards; specifically, clause 8.1.9 of HG/T 20512-2014 contains a table that specifies the installation spacing for instrument cables and power cables. The installation distance for power cables and instrumentation cables with a voltage range of 200V~400V and a current capacity of 100A is 200mm. I think that although the electric valve operates at 380V, the cable can only handle 1A of current; therefore it’s not possible to follow the requirements specified in the table. Those requirements include current limits. May I reply by saying that although the voltage is 380V, the current is very low, so it does not meet the requirements outlined in the standards?
Although it is an instrumentation device, 380V cables should not be placed in the same tray as signal cables. Even though the current level is low, such cables still belong to the category of power cables; signal cables are particularly sensitive to induced voltages. It is recommended to make the necessary adjustments as required by the client.
The signal cable features aluminum foil shielding for the split-screen and main screen.
This post was last edited by t*ngtou on 2016-7-18 08:23. I encountered this problem when the factory was built years ago; it was carried out by Sanhua Jian. They came up with a standard for that purpose, and I still remember clearly those accompanying illustrations – there was a partition placed between the two wires; I can’t recall whether the thickness of that partition was 1.5 mm or 15 mm. It’s not clear how it was negotiated with the manager in the end; anyway, the wire remains the same when driving normally.
In the instrumentation departments of various design institutes, are the power supply cables for electric valves always designed to use separate cable trays? Is it laid separately from the 24V control wire and signal wire? That’s impossible; from what I know, it’s enough to add partitions.
Thank you. It’s just that the cables have already been installed, so making corrections is very troublesome.
In our offshore projects, all power cables and instrument signal cables with a voltage of over 100V must be routed in separate cable trays; this issue needs to be rectified.
Actually, it’s not a big deal; since the current flowing through the power supply of the electric valve is low, there’s little impact from having it run along with the signal cable. Power cables generally refer to those used by large electrical devices, such as pumps and welding machines. But the regulations are fixed; it is possible to discuss matters with the property owner and work together, and if there is indeed interference, then take action to address it.
It’s not allowed according to the specifications, but there are no issues in actual operation; moreover, electric valves are operated intermittently.
It is powered by 380V, along with instrument signals (24V control wires and 4–20mA signal wires; all of these go to the DCS. According to the specifications, the responsibility for design lies within the electrical engineering team – so why do all these signals go to the DCS?