Feeder Terminal Unit

This device can connect to SCADA System and DMS, and you can connect the terminal to the server according to your local network conditions. This terminal supports CDMA (3G)/LTE (4G)/ NR（5G）, ETH, fiber optic and other ways to access the network. You can also contact us directly, and we will provide you with a solution for distribution network automation.

Three-Section Overcurrent Protection is a coordinated protection scheme widely used in power systems to detect and isolate faults (e.g., short circuits) while ensuring selective tripping. It consists of three stages with distinct operating characteristics based on current magnitude and time delay:

1. Instantaneous Overcurrent Protection (Section I)

Function: Responds immediately to severe overcurrents exceeding a high-set threshold (e.g., 5–10 times the rated current).

Purpose: Rapidly clears close-in faults (near the protection device) to prevent equipment damage.

Key Feature: No intentional time delay (operates in milliseconds).

2. Time-Delayed Overcurrent Protection (Section II)

Function: Triggers after a predefined short delay (e.g., 0.1–0.5 seconds) for moderate overcurrents (e.g., 2–5 times the rated current).

Purpose: Handles faults farther from the protection device, allowing downstream breakers to clear localized faults first (selectivity).

Coordination: Employs a time-graded scheme—higher fault currents (closer faults) trip faster, while lower currents (remote faults) trip slower.

3. Backup Overcurrent Protection (Section III)

Function: Activates after a longer time delay (e.g., several seconds) for low-magnitude overcurrents (e.g., 1.2–2 times the rated current).

Purpose: Serves as a backup for primary protection (Sections I/II) and addresses overloads or persistent faults.

Characteristic: May use an inverse-time curve (trip time decreases as current increases).

Coordination Principle

The three sections work hierarchically:

Section I clears severe faults instantly.

Section II handles moderate faults with short delays, prioritizing system selectivity.

Section III provides backup protection, ensuring reliability if upstream protections fail.

This layered approach minimizes outage scope, balances speed and selectivity, and enhances grid stability.

This protection device supports 2-channel serial data communication, RS232 or RS485 bus, independent of each other. It can be configured separately. The configuration method is as follows:

1. Enter the settings page: Edit → Para;
2. Configure communication function on/off: Scroll down and find Comm1 Status set to 1, indicating it is turned on, and 0 indicates it is turned off. The default setting is open;
3. Set communication baud rate: According to the baud rate configuration of RTU or protocol converter, the default value is 9600;
4. Set communication protocol: There are four protocols to choose from, corresponding to setting 1 as IEC-60870-101, setting 2 as IEC-60870-104, setting 3 as DNP3.0, setting 4 as ModBus-RTU, default as IEC-60870-101;
5. Set communication balance (only valid for multiple IEC-60870-101): Set 1 to IEC-60870-101 protocol balance mode and 0 to imbalance mode;
6. Set the communication source address: Set the value to 1-65535, default value to 1;
7. Set the target address for the report: set the value to 0-65535, default value to 1;
8. Set active upload: 0 does not actively upload, 1 actively uploads, default value is 1;
9. Save settings: After completing the settings, press the "Enter" key, enter the password 0099 (some models are 0077), press the "Enter" key again, and the screen will prompt "Save successful", indicating that the settings have been saved.

At this point, channel 1 has been established, and channel 2 is established in the same way as channel 1.

NOTE: 1. The product has been set to default settings before delivery to meet most usage scenarios. It is not recommended to make modifications or only modify controllable items (such as modifying communication protocols, configuring communication functions on/off, etc.) when it can be used normally