Description
Overview of Digital Multifunction Protective Relay
- The ASL-591H Microprocessor-Based Comprehensive Protection Device, a digital multifunction protective relay, is suitable for the comprehensive protection of 10 kV and below incoming and outgoing lines in ring main units and gas-insulated switchgear, as well as 380 V low-voltage incoming and outgoing lines in distribution rooms.
Features of Numerical Protection Relay
- This multifunction protection relay is suitable for plant service transformers, power supply feeders and bus tie protection at 10 kV and below. It supports AC/DC 220 V and DC 110 V power supplies (24 V/48 V available on request). Featuring a compact design, it is easy for instrument room installation.
Functions of Digital Multifunction Protection Relays
- Two-stage overcurrent protection (instantaneous current tripping & definite-time overcurrent), each stage can be independently enabled or disabled;
- Overload protection: output configurable for tripping or alarm;
- Zero-sequence overcurrent protection: output configurable for tripping or alarm;
- Inverse-time overcurrent protection: fixed output for tripping;
- Non-electrical protection: heavy gas tripping (transformer door interlock), over-temperature tripping, light gas alarm, over-temperature alarm, etc.
Event Logging Function of Digital Multifunction Protection Relay
- The log records events including protection trip events, alarm events, and device self-test failures;
- It records the type and time of protection trip events, as well as the type and time of device self-test failures.
Numerical Protective Relays – Communication Functions
- Upload real-time data, including measurement data, fault alarm signals, and protection settings.
- Receive control commands from higher-level systems.
Communication Interface
- This device provides a high-speed, reliable RS-485 interface for external communication. It supports the standard MODBUS protocol.
Rated DC Specifications
- Voltage: 220 V, 110 V;
DC voltage ripple factor: ≤2%; voltage fluctuation: 80–115% of rated voltage
Rated AC Specifications
- Rated AC current In: 5 A, 1 A;
- The AC power waveform is sinusoidal, with a distortion factor not exceeding 2%;
- Frequency fn: 50 Hz (60 Hz option available; specify when ordering), with a tolerance of ±0.5%.
Dimensions of Numerical Protection Relays

Multifunctional Protection Relay Setting Sheet
| No. | Name | Range | Step | Remarks |
|---|---|---|---|---|
| 1 | Stage 1 Protection Setting (Instantaneous Current Trip) | |||
| 1.1 | Stage 1 Protection Enable | 1/0 | — | Stage 1 protection: Enable(1) / Disable(0) |
| 1.2 | Stage 1 Time Delay | 0~120.00s | 0.01s | |
| 1.3 | Stage 1 Setting Value | 0.40~99.99A | 0.01A | |
| 2 | Stage 2 Protection Setting (Definite-time Overcurrent) | |||
| 2.1 | Stage 2 Protection Enable | 1/0 | — | Stage 2 protection: Enable(1) / Disable(0) |
| 2.2 | Stage 2 Time Delay | 0~120.00s | 0.01s | |
| 2.3 | Stage 2 Setting Value | 0.40~99.99A | 0.01A | |
| 3 | Overload Setting | |||
| 3.1 | Overload Protection Enable | 1/0 | — | Overload protection: Enable(1) / Disable(0) |
| 3.2 | Overload Trip Mode | 1/0 | — | Overload: Trip(1) / Alarm(0) |
| 3.3 | Overload Time T | 0~120.00s | 0.01s | |
| 3.4 | Overload Current I | 0.40~99.99A | 0.01A | |
| 4 | Zero-sequence Overcurrent Setting | |||
| 4.1 | Zero-sequence Overcurrent Enable | 1/0 | — | Zero-sequence overcurrent protection: Enable(1) / Disable(0) |
| 4.2 | Zero-sequence Overcurrent Trip Mode | 1/0 | — | Zero-sequence overcurrent: Trip(1) / Alarm(0) |
| 4.3 | Zero-sequence Time Delay | 0~120.00s | 0.01s | |
| 4.4 | Zero-sequence Setting Value | 0.5~99.99A | 0.01A | |
| 5 | Inverse-time Overcurrent Setting | |||
| 5.1 | Inverse-time Overcurrent Enable | 1/0 | — | Inverse-time overcurrent protection: Enable(1) / Disable(0) |
| 5.2 | Inverse-time Time Constant T | 0.1~120.00s | 0.01s | Time constant of inverse-time overcurrent protection |
| 5.3 | Inverse-time Current Setting I | 1~10A | 0.01A | Setting value of inverse-time overcurrent protection |
| 6 | Non-electrical Protection Setting | |||
| 6.1 | Non-electrical Protection 1 Enable | 1/0 | — | Non-electrical protection 1: Enable(1) / Disable(0) |
| 6.2 | Non-electrical Protection 1 Trip Mode | 1/0 | — | Non-electrical protection 1: Trip(1) / Alarm(0) |
| 6.3 | Non-electrical Protection 2 Enable | 1/0 | — | Non-electrical protection 2: Enable(1) / Disable(0) |
| 6.4 | Non-electrical Protection 2 Trip Mode | 1/0 | — | Non-electrical protection 2: Trip(1) / Alarm(0) |
| 6.5 | Non-electrical Protection 3 Enable | 1/0 | — | Non-electrical protection 3: Enable(1) / Disable(0) |
| 6.6 | Non-electrical Protection 3 Trip Mode | 1/0 | — | Non-electrical protection 3: Trip(1) / Alarm(0) |
| 6.7 | Non-electrical Protection 4 Enable | 1/0 | — | Non-electrical protection 4: Enable(1) / Disable(0) |
| 6.8 | Non-electrical Protection 4 Trip Mode | 1/0 | — | Non-electrical protection 4: Trip(1) / Alarm(0) |
| 6.9 | Non-electrical 1 Time Delay | 0.1~120.00s | 0.01s | |
| 6.10 | Non-electrical 2 Time Delay | 0.1~120.00s | 0.01s | |
| 6.11 | Non-electrical 3 Time Delay | 0.1~120.00s | 0.01s | |
| 6.12 | Non-electrical 4 Time Delay | 0.1~120.00s | 0.01s | |
| 6.13 | Non-electrical Parameter Value | 0000~FFFF | — | |
| 7 | General Setting | |||
| 7.1 | Three-element Wiring Enable | 1/0 | — | Three-element wiring: Enable(1) / Disable(0) |
| 7.2 | Current Transformation Ratio | 0~9999 | 1 |
FAQ
Q:How are comprehensive protection relays typically installed and used, and what types of equipment can they protect?
A:Compact comprehensive protection devices are suitable for installation in ring main units and high-voltage switchgear. With control in numerical protection relay integrated, they provide complete protection for feeders, feeder terminals, distribution transformers and small motors.











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