Electrical problem in operation of waste water treatment station

Operating a wastewater treatment system is not simple and is divided into several stages. In order to ensure effective operation, it is required that the operation technician must understand the operating process of the system. There should be a plan for operation, maintenance, and inspection of systems, equipment, machines, micro-organisms, treatment tanks, filtration and disinfection systems, etc. Therefore, the operation of the wastewater treatment system requires Operators must have expertise and experience in wastewater treatment.

Due to many factors, during the operation, many times technical staff encountered some problems with the wastewater treatment system. One of the many reasons is the lack of electrical expertise among operators. Here, we invite you to join VESACO to learn about some causes and ways to fix problems with the electrical system during the operation of the wastewater treatment system.

Before going into understanding the common problems and causes with the solar power system, we need to understand the basic components of an electrical system including:

– Central control cabinet.

– Electrical cabinets for measuring equipment, sump electrical cabinets, electrical connection cabinets.

– Cable tray ladder system, protection pipes, electric cables.

Central control cabinet

Usually made of powder coated steel, stainless steel. Wall mount or stand. The cabinet can be placed indoors or outdoors.

The function of the central control cabinet is to provide power, protect and control – monitor the operation of all equipment in the system. The cabinet has the following main components:

– Switching equipment: Aptomat, Contactor, Thermal Role

– Control device: PLC or timer

– Auxiliary equipment: Intermediate role, indicator light, push button, switch switch, headlight indicator….

To better understand the structure and function of the equipment in the control panel of the wastewater treatment station, please review the article below:

Electrical cabinets for measuring equipment, sump electrical cabinets, electrical connection cabinets

These electrical cabinets are usually located outdoors, used to mount the display unit of measuring devices or control power supply with 1 or 2 sump pumps, to connect between the electrical cord drawn from the central cabinet and the power cord. of equipment such as submersible pump, submersible stirrer….

Cable tray ladder system, protection pipes, electric cables

Electrical cables in wastewater treatment systems have the function of transmitting electricity or control signals from electrical cabinets to equipment. Consists of copper or aluminum conductive core and PVC, XLPE, DSTA…

The system of cable tray ladders and protective pipes has the function of supporting and protecting the electrical cable system from external impacts. Usually made of powder coated steel, corrugated iron or fireproof plastic.

After understanding the basic components, we will go into understanding the signs, causes and solutions to errors in the electrical system of the wastewater treatment plant.

1. Switchboard has phase loss, phase reversal, or voltage breakdown


  – The phase indicator light on the electrical cabinet does not light up (Phase loss).

– Voltmeter does not indicate (Phase loss) or display value is higher than rated (Voltage breakdown).

– The equipment in the system does not work (Loss of 2 or 3 phases), sounds loud or vibrates abnormally, rotates in the opposite direction from the design (Phase reversal or voltage breakdown).

– Role system protects the phase of the active switchboard.


– Due to errors in the repair process, connect the power supply to the system.

– Due to breakdown of switchgear, transformer or transmission cable system.

– Due to incorrect calculation of transformer capacity, power supply leads to voltage drop.

How to check and fix

– Use a dedicated meter to accurately determine the problem you are experiencing.

– Check phase order, reconnect correctly.

– Adjust the transformer capacity, increase the size of the power supply conductor to the system.

2. Electrical cabinet lost control power


– The power supply to the electrical cabinet is still guaranteed.

– The equipment in the electrical cabinet such as indicator lights, control screen, PLC.. does not work.

– Devices in the system are not working.


– Fired control fuse, damaged control Aptomat.

– The E-Stop button is accidentally impacted.

– Damage to 24VDC power supplies or power transformers.

How to check and fix

– Check and return the initial state for the E-Stop button.

– Use a dedicated meter to measure and replace if damaged 24VDC power supplies or power transformers.

– If the control fuse is burned or the control Aptomat operates, it is necessary to conduct a detailed check of the control circuit system to determine the location of short-circuit, damage to repair and replace.

3. The motor is overloaded, phase lost, case hit


– The engine does not work, or operates with abnormally high temperatures, loud noises, and vibrations.

– Aptomat, Role thermal impact.

– Motor inverter error (if any).

– The Fault indicator light on the cabinet door is on.


– Wrong engine selection, wrong capacity calculation.

– The power supply to the motor is not guaranteed, not in accordance with the rated voltage, phase loss, phase reversal. Due to faulty switchgear or conductors.

– Engine stuck load, damaged bearings, bearings.

– The motor operates in an overheated environment, leading to damage to the winding insulation, touching the shell and burning the motor.

– The engine is operating in a humid environment or water gets inside the engine leading to the case.

How to check and fix

– Use a dedicated meter to check the winding resistance, insulation resistance of the motor and repair if there is damage.

– Check the power supply to the motor, re-tighten the cos head and connection positions

– Check if the motor is stuck or not.

– Check the status of the switchgear.

– Check the motor current at no-load and load, compare with rated current. Determine the exact power required for the device.

– Make sure the engine operates in an environment with permissible temperature and humidity.

4. Device does not work Auto /Man


– The device does not run automatically according to the program installed on the PLC or the time on the timer after switching the Switch state to Auto.

– The device does not work after switching the Switch state to Man.


– The electrical cabinet has lost phase, reversed phase or lost control source.

– Aptomat, the thermal role of the device is affected by the motor being overloaded, losing phase, touching the shell

– Due to PLC or timer damage, control program error.

– Due to insufficient conditions to meet operating conditions according to the control program such as float condition, time condition, signal from sensor or switch switch failure.

How to check and fix

– Check the power source, the control source of the electrical cabinet.

– Check if the Thermal Role, Aptomat of the device is active or not. If yes, check the condition of the motor, wiring and repair.

– Check the error code of the inverter. Follow the manufacturer’s instructions to identify the fault and correct it.

– Check the operation status of PLC, timer.

– Re-check the response conditions to operate according to the control program (conditions on time, level indicator, PH sensor, switching switch…). The device may not work because it has not met all the necessary conditions or due to damage to the sensor, level indicator, replace if necessary.

5. Damage to the system of cable trays, protection pipes, conductors


– Cable tray ladder system is peeling, rusting, abnormal heat increase.

– Aptomat, the thermal relay of the device works, the device cannot work because the power supply wire is shorted, phase lost.

– The signal transmission lines from the sensor to the electrical cabinet have problems.


– Due to choosing the wrong type of cable tray ladder, protective pipe (Material, size), not suitable for the purpose of use and working environment.

– Arrangement of too many conductors in the cable tray, protection tube leads to excessive heat generation, damage to the wiring system.

– Due to not conducting earth drain connection, causing heat generation and interference with control signals.

– Due to not sealing the open positions after complete installation, rats can follow and damage the wire.

– Due to the wrong choice of conductor for the working environment.

How to check and fix

– Check and replace the power cable to the correct working environment. 

– Check and replace cable trays and protective pipes that meet the following criteria:

  • Number of cables.
  • Outer dimensions of the conductor.
  • Allowable bend radius of cable.
  • Total cable weight.
  • Space for installation.

– Select materials for manufacturing cable trays and protective pipes according to the following criteria:

  • Fireproof PVC: Indoor.
  • Powder coating: For indoor use.
  • Electrolytic galvanizing: Used in homes and places less affected by the environment.
  • Hot dipped galvanized: Used outdoors, marine environment.

– Conduct grounding to connect the trough and use foam glue, silicone to seal the ends of pipes, gaps on cable trays.

6. Damage to the system of connection cabinets, measuring equipment, sumps


– The equipment at the sump, the measuring device does not work or works incorrectly.

– Aptomat, Thermal Role of the actuating device.


– Due to the design and selection of materials, improper installation leads to moisture causing equipment damage.

How to check and fix

– Check the humidity. rust condition of the cabinet cover, equipment installed in the cabinet.

– Select and replace materials to suit the installation location.

– Use materials that meet water-resistant standards in outdoor or under-tank locations.

Through the article, we have mentioned the common problems and their causes and how to fix them so that you can check in the operation of the wastewater treatment system. With 15 years of experience, VESECO confidently shares knowledge to help you be more confident in operating wastewater treatment plants. If you need to renovate, maintain and maintain your systems, please contact us.

Head Office – Vietnam Water and Environmental Sanitation Co., Ltd

Address: 2nd Floor, Building D, Viet Duc Complex, Alley 164 Khuat Duy Tien, Thanh Xuan, Hanoi City, Vietnam

Hotline: (+84) 904 571 488.