610H Small Current Grounding Line Selection Device

Description

What Is a Small Current Grounding Line Selection Device?

Specifically designed for neutral ungrounded or resonant-grounded systems, the low current grounding line selection device—commonly known as a grounding line selection device—accurately identifies the faulty feeder among multiple outgoing lines when a single-phase-to-ground fault occurs. By overcoming the line-selection challenge posed by weak fault currents and elusive signals, it enables rapid fault isolation, prevents arc-induced fires, minimizes outage scope, and ultimately ensures safe and reliable grid operation.

How Does a Small Current Grounding Line Selection Device Work?

The device continuously monitors zero-sequence signals generated during single-phase-to-ground faults in neutral ungrounded or resonant-grounded systems. By analyzing these signals, it pinpoints the faulted feeder and initiates appropriate protection actions.

Zero-Sequence Current Measurement

The device uses CTs on each outgoing feeder to measure zero-sequence current—the vector sum of three-phase currents. Under fault conditions, the faulted feeder carries the highest zero-sequence current, serving as the primary indicator for line selection.

Zero-Sequence Voltage Detection

VTs on the system bus detect zero-sequence voltage, which rises sharply from near zero when a ground fault occurs. This voltage increase triggers the selection process and provides critical phase reference for fault analysis.

Fault Current and Phase Analysis

The device compares the phase relationship between zero-sequence current and voltage. In ungrounded systems, faulted line currents are in phase opposition to healthy ones; in resonant-grounded systems, additional transient or harmonic analysis is used to overcome compensation effects.

Faulted Line Identification

Using magnitude comparison, phase polarity, and advanced algorithms (e.g., transient analysis, harmonic injection), the device determines which feeder is faulted. Voting and correlation checks ensure high reliability and reject noise-induced errors.

Alarm and Trip Output

Once identified, the device outputs alarms for operator awareness and can issue trip commands to isolate the faulted feeder. Communication via SCADA protocols enables remote monitoring and integration with distribution management systems.

Applications of Small Current Grounding Line Selection Devices

These devices are deployed across medium-voltage networks with ungrounded or resonant-grounded neutrals to enable rapid faulted feeder identification, ensuring service continuity, equipment protection, and operational safety. Key application areas include:

10kV Distribution Systems

The most common application, as 10kV networks typically adopt low-current grounding. With long feeders and numerous branches, the device swiftly isolates faults, preventing escalation and minimizing customer outage minutes.

20kV and 35kV Distribution Networks

Higher capacitance and fault currents demand more sophisticated algorithms. The device reliably pinpoints faults in long-distance or heavily branched feeders, maintaining safety and enabling quick service restoration.

Substations

Installed at busbar or feeder panel level, the device provides clear fault indication for operators, reduces diagnosis time, and integrates with SCADA for centralized monitoring in automated or unmanned substations.

Industrial Power Systems

In petrochemical, steel, mining, and manufacturing plants, the device quickly locates faults amid high noise and switching transients, preventing production stoppages, equipment damage, and arc flash hazards.

Power Plants

Monitoring auxiliary 6kV or 10kV feeders, the device protects generators and station-service transformers by providing early warning and selective tripping, ensuring high plant availability even in EMI-rich environments.

Renewable Energy and Distribution Systems

In solar, wind, and battery storage plants, the device isolates faults in collector networks while keeping healthy feeders online, supporting remote reporting and coordination with grid protection for reliable renewable integration.

How to Select a Small Current Grounding Line Selection Device

Small Current Grounding Line SelectionFeatures

Category	Function Item	Core Specification
Grounding Line Selection Function	Transient Line Selection	Adopts transient route selection method
Grounding Line Selection Function	Zero-sequence Directional Line Selection	Adopts zero-sequence overcurrent directional selection method
Grounding Line Selection Function	PT Monitoring & Protection	Supports PT de-resonance and PT open-circuit monitoring
Grounding Line Selection Function	Reclosing & Acceleration Protection	Equipped with reclosing function and post-reclosing acceleration protection
Device Self-Test Function	Hardware Fault Detection	Automatically detects RAM, FLASH, A/D, power loss and other hardware faults
Device Self-Test Function	Parameter Validity Check	Automatically verifies setpoints, configuration parameters, coefficients and other settings
Communication Function	Communication Interface Support	Supports RS-485, RS-232, Ethernet and IEC 61850 communication modes (specify when ordering)
Communication Function	Real-time Data Upload	Can upload busbar voltage, current, grounding information, harmonic data and other real-time operating data
Communication Function	Remote Control & Command Reception	Can receive remote control, system synchronization and other control commands from the upper-level system
Panel & Operation Function	Human-machine Interface	Equipped with Chinese character LCD display, status indicator lights and keypad for easy monitoring and operation
Time Synchronization Function	Network Time Sync	Supports network-based time synchronization via communication channels
Time Synchronization Function	IRIG-B Code Sync	Supports IRIG-B code time synchronization

Rated Electrical Parameters

Category	Parameter Name	Specification Requirements
Power Supply Specifications	Rated Operating Voltage	AC/DC 220 V
Power Supply Specifications	Permissible Voltage Deviation	-20% ~ +15%
Power Supply Specifications	Ripple Factor	≤5%
AC Circuit Specifications	AC Rated Current In	1 A/5 A
AC Circuit Specifications	AC Rated Voltage Un	100 V
AC Circuit Specifications	Rated Operating Frequency	50 Hz
Power Consumption Specifications	DC Power Circuit Power Consumption	≤25 VA during normal operation; ≤30 VA when the device is activated
Power Consumption Specifications	AC Voltage Circuit Power Consumption	≤1 VA per phase at rated voltage of 100 V
Power Consumption Specifications	AC Current Circuit Power Consumption	≤0.5 VA per phase at rated current of 1 A; ≤1 VA per phase at rated current of 5 A

Small current grounding line selecting device Mechanical Installation Dimensions Drawing

• Dimensions: Width × Height × Depth = 484 × 177 × 285 (mm)
• Mounting hole dimensions: 445 × 177 (with 4 mounting holes, each 6.5 mm in diameter)

Small Current Grounding Line Selection Device Fixed-Price Order

No.	Display Name	Range	Step	Remark
1	Bus Setting			Bus I setting Bus II / Bus III / Bus IV are consistent with Bus I
1.1	Name	M001~M004	1
1.2	PT Ratio	1-1000	—
1.3	PT Disconnection	Enable / Disable	—
1.4	Outlet Quantity	—	—
1.5	Earth Fault Trip	Enable / Disable	—	Enable for trip, Disable for alarm
1.6	Earth Fault Time Delay	0.1S	0.1S
1.7	Post Acceleration	Enable / Disable	—	Need to set acceleration time if enabled
1.8	Earth Fault Voltage	5.0～100.0V	0.1V
1.9	Rotation Control	Enable / Disable	—
1.10	Voltage Threshold	0.1～100.0V	0.1V
1.11	Voltage Dead Zone	0.1～100.0V	0.1V
1.12	Rotation Mode	Auto / Fixed	—	Auto rotation mode / Fixed rotation mode
1.13	Rotation Time Delay	0.1S	0.1S
1.14	PT Blocking Earth Protection	Enable / Disable	—	Block earth protection when PT disconnection occurs
1.15	Rotation Voltage	5.0～100.0V	0.1V
1.16	Corresponding Bus Number	1-4	—
1.17	Permanent Fault Time Delay	0～100.0S	0.1S
1.18	Spare	Enable / Disable	—
1.19	Current Threshold	5～100mA	1mA
1.20	Spare	Enable / Disable	—
1.21	Current Dead Zone	5～100mA	1mA
1.22	Spare	Enable / Disable	—
1.23	Spare	Enable / Disable	—
2	Feeder Setting			Feeder No.01 Other feeders follow the same setting
2.1	Name	Line I B001	—
2.2	Line Type	Overhead / Cable / Station Internal	—
2.3	Line Trip Output No.	—	—
2.4	CT Ratio	1～1000	—
2.5	CT Polarity	Positive / Reverse	—
2.6	Transient Earth Fault Setting	5～100mA	1mA
2.7	Earth Delay High Byte	0～100.0S	0.1S
2.8	Line Earth Fault Trip	Enable / Disable	—	Trip when enabled, alarm when disabled
2.9	Earth Fault Current	5～100mA	1mA
2.10	Spare	—	—
2.11	Earth Delay Low Byte	0～100.0S	0.1S
2.12	Rotation Control	Enable / Disable	—	Participate in rotation if enabled
2.13	Rotation Sequence	1-4	—
2.14	Line Closing Output No.	—	—
2.15	Auto-reclosing Enable	0 / 1	—
2.16	Protection Trigger Reclosing	0 / 1	—
2.17	Reclosing Time Delay	0～100.0S	0.1S
3	Spare Setting	—	—
4	Resonance Threshold Setting
4.1	Spare	5.0～100.0V	0.1V
4.2	Spare	5.0～100.0V	0.1V
4.3	17Hz Resonance Threshold	5.0～100.0V	0.1V
4.4	25Hz Resonance Threshold	5.0～100.0V	0.1V
4.5	50Hz Resonance Threshold	5.0～100.0V	0.1V
4.6	150Hz Resonance Threshold	5.0～100.0V	0.1V
4.7	250Hz Resonance Threshold	5.0～100.0V	0.1V
4.8	Overvoltage Threshold	5.0～100.0V	0.1V
5	Binary Input Setting
5.1	Debounce Time Delay	10ms～9999ms	—	Factory default: 20ms
	Remote Signal Polarity 1～48	0 or 1	—
6	LCD Setting
6.1	Fault Lamp Reset Mode	Auto / Manual	—
6.2	Fault Lamp Return Time	0～120S	1s

FAQ

1. What is a small current grounding line selection device?

A small current grounding line selection device is a protection and fault-detection device used to identify the faulted feeder when a single-phase-to-ground fault occurs in a low-current grounding system. It analyzes electrical signals such as zero-sequence current and voltage to determine which outgoing line is experiencing the grounding fault.

2. What is a small current grounding system?

A small current grounding system is a power distribution system in which the grounding fault current is relatively low. Common grounding arrangements include ungrounded, resonant-grounded, and other low-current grounding configurations. Because the fault current can be difficult to distinguish from normal system currents, dedicated fault line selection equipment may be required.

3. What does a grounding line selection device detect?

The device is primarily used to detect and identify the feeder associated with a single-phase grounding fault. Depending on the system configuration and device design, it can analyze zero-sequence current, zero-sequence voltage, transient components, phase relationships, and other electrical characteristics.

4. How does a small current grounding line selection device work?

The device collects grounding-related electrical signals from multiple outgoing feeders and analyzes their characteristics. By comparing zero-sequence quantities and other fault indicators, the protection algorithm determines the most likely faulted feeder and provides an alarm, indication, communication signal, or trip output according to the system configuration.

5. Can it identify the faulted feeder in a 10kV distribution system?

Yes. Small current grounding line selection devices are commonly applied to medium-voltage distribution systems where single-phase grounding faults may occur with relatively small fault currents. The actual applicable voltage level, feeder configuration, CT arrangement, and grounding method should be confirmed according to the project requirements.

6. What is the difference between ground fault protection and grounding line selection?

Ground fault protection is primarily intended to detect an abnormal ground-fault condition and initiate an alarm or trip. Grounding line selection goes one step further by identifying which outgoing feeder is most likely associated with the grounding fault. Therefore, a grounding line selection device can be particularly useful in systems with multiple outgoing feeders.

7. What signals are required for grounding line selection?

The required signals depend on the protection method and system configuration. Typical inputs may include zero-sequence current, zero-sequence voltage, phase voltage, and other electrical quantities used by the fault-selection algorithm. CT and PT/VT arrangements should be selected according to the specific grounding system.

8. Can the device be used for intermittent or transient grounding faults?

The capability depends on the protection algorithm and product configuration. Some grounding line selection systems use transient fault characteristics in addition to steady-state electrical quantities, which can improve fault identification when the grounding current is small or unstable.

9. What is the difference between a small current grounding line selection device and a ground fault relay?

A ground fault relay generally focuses on detecting ground-fault current or voltage and providing protection output. A small current grounding line selection device is designed specifically to determine the faulted feeder in a low-current grounding network. In multi-feeder distribution systems, line-selection functionality can provide more detailed fault information than a basic ground-fault detection function.

10. Where are small current grounding line selection devices used?

Typical applications include medium-voltage distribution networks, substations, industrial power systems, power plants, and other electrical systems using low-current grounding methods. They are especially useful where operators need to quickly identify the affected feeder without manually checking multiple outgoing lines.

11. How do I select the right grounding line selection device?

Selection should consider the system voltage, grounding method, number of outgoing feeders, CT/PT configuration, fault-detection method, required communication interfaces, installation method, and required alarm or trip outputs. For a project-specific selection, the system single-line diagram and basic electrical parameters should be reviewed before choosing the device.

12. Can the grounding line selection device communicate with a SCADA system?

Depending on the product configuration, communication interfaces can be provided for integration with substation automation or SCADA systems. The available communication protocol, physical interface, data points, and network architecture should be confirmed according to the selected model.

13. What information should I provide when requesting a quotation?

For accurate product selection, it is recommended to provide the system voltage, grounding method, number of outgoing feeders, CT/PT information, protection requirements, communication requirements, installation conditions, and the required quantity. A single-line diagram is also helpful for engineering evaluation.

14. Can you provide technical support for grounding line selection projects?

Yes. Project-specific technical support can include product selection, configuration recommendations, application guidance, and assistance with the required electrical parameters. Customers can provide their system information or single-line diagram for a more accurate recommendation.