Kehui ZDT-300 DC Earth Fault Locator

The Kehui ZDT-300 DC Earth Fault Locator is used to quickly and accurately locate DC network earth faults on live systems. In electrical power installations, the DC system is an important part, and any earth faults can affect the operation of vital components such as system protection, circuit breakers, and communication equipment. The correct operation of the DC system is, therefore vital to the stability of the network.

The Kehui ZDT-300 DC Earth Fault Locator comprises a signal transmitter, receiver, and sensors for different cable sizes. Depending on the model chosen, the system can detect high resistance faults up to 1MΩ, allowing problems to be identified early so that remedial action can be taken to prevent a subsequent failure. Some of the key features of the ZDT-300 DC Earth Fault Locator include:

• Detection of DC network earth faults on a live system
• Automatic identification of positive and negative DC bus voltages
• Detection of AC interference on the battery system
• Measurement of fault resistance, capacitance to earth, and balance resistance
• The transmitter power is taken directly from the system, an external supply is only required if the system voltage is too low
• High sensitivity, up to 1MΩ fault detection capability

In this article, we will explore the importance of DC earth fault location, the working principle of the ZDT-300 DC Earth Fault Locator, its applications, and its advantages over other fault location technologies.

Importance of DC Earth Fault Location

The DC system is a floating unearthed system, meaning an earth fault on one terminal will not prevent the system from working normally. However, if an earth fault occurs simultaneously on the other terminal, it will result in a virtual short-circuit between them through the earth, causing the failure of the DC supply. Therefore, it is crucial to quickly and accurately locate DC network earth faults on live systems to prevent subsequent failures and ensure the stability of the network.

Tracing earth faults in offline conditions can interrupt the functioning of critical control circuitry, which is why it is highly recommended to have an online DC Earth Fault Locator to find out the faults on the line. The Kehui ZDT-300 DC Earth Fault Locator is designed to provide a reliable and efficient solution for detecting and locating DC network earth faults on live systems.

Working Principle

The Kehui ZDT-300 DC Earth Fault Locator works by injecting an AC VLF (Very Low Frequency) signal into the DC system using its transmitter unit. The receiver unit then tracks the injected signal, allowing the user to locate the fault accurately. The low voltage (24V) and low current (50µA) injected by the Kehui ZDT-300 DC Earth Fault Locator are safe compared to existing DC earth fault locating technologies worldwide.

One of the challenges in DC earth fault location is the capacitive nature of the DC system control cables, which can mimic fault conditions due to capacitive leakage current. The ZDT-300 DC Earth Fault Locator overcomes this difficulty by performing automatic capacitance balancing, ensuring accurate fault detection even in capacitive leakage currents.

Applications

The Kehui ZDT-300 DC Earth Fault Locator is widely used in various industries and applications where DC systems are present. Some of its common applications include:

• Power plants
• Substations
• Telecommunication networks
• Industrial processes
• Renewable energy systems

In these applications, the Kehui ZDT-300 DC Earth Fault Locator plays a crucial role in ensuring the reliable and efficient operation of the DC systems by detecting and locating earth faults at an early stage.

Advantages

Compared to other fault location technologies, the Kehui ZDT-300 DC Earth Fault Locator offers several advantages, including:

• High sensitivity, up to 1MΩ fault detection capability, allowing for early detection of problems
• Automatic identification of positive and negative DC bus voltages, simplifying the fault location process
• Detection of AC interference on the battery system, ensuring accurate fault detection
• Measurement of fault resistance, capacitance to earth, and balance resistance, providing valuable information for troubleshooting
• The transmitter power is taken directly from the system, reducing the need for external power supplies
• These advantages make the ZDT-300 DC Earth Fault Locator a reliable and efficient tool for detecting and locating DC network earth faults on live systems, helping to prevent subsequent failures and ensure the stability of the network.

Kehui ZDT-300 DC Earth Fault Locator Specifications:

General

• Application to DC system voltage level: 24V, 48V, 110V, 220V
• Maximum distributed capacitance value to earth: branch ≤47uF, total ≤150uF
• Earth resistance range: 0-1MΩ (depending on version selected)
• Environmental conditions:
• Temperature -10oC to +50oC
• Humidity 5-90% RH
• Ingress protection IP54

Transmitter

• Output voltage: 1000V, 500V or 250V (depending on version selected)
• Output frequency: 0.1 – 0.5Hz (automatically determined)
• Power supply: DC（220V/110V）or AC 220V
• Dimension: 195mm×112mm×65mm, weight: 0.80kg

Receiver

• Power supply: 7.2V rechargeable lithium battery, up to 20 hours continuous operation
• Dimension: 195mm×112mm×45mm, weight: 0.55kg

Clamp

• Power supply: 2×AA battery, up to 20 hours continuous operation
• Dimension: 180mm×60mm×35mm; Weight: 0.21kg

Current sensor

• Replaces the current clamp for large diameter cables
• Connects directly to the receiver
• Dimension: 130mm×180mm×30mm; Weight: 0.20kg