Overview
The AM3SE series is Acrel’s cost-effective numerical protection relay designed for user terminal substations up to 35kV.
Integrating protection and control functions, it features mature protection principles, an industrial-grade hardware platform, 11 digital inputs, 5 relay outputs, and 1 RS485 communication port.
The series includes current type (AM3SE-I) and voltage type (AM3SE-U), which can be flexibly configured for feeders, bus couplers, distribution transformers, etc.—an ideal choice for building unmanned substation distribution automation systems.
Highlight
Mature Protection Functions
- 3-stage O/C, inverse, zero-seq, negative seq
- Recloser, UFLS, post-acceleration
- Non-electric & voltage alarms (U type)
Industrial-grade EMC
- Level IV immunity (EFT, ESD, Surge)
- Wide temp: -10°C to +55°C
- High insulation: >100MΩ
Customizable Digital Inputs
- 11 DI freely mapped to status/non-electric
- Supports breaker positions, remote, etc.
- Simple code-based configuration
Dual-Protocol Communication
- Modbus-RTU & IEC60870-5-103 switchable
- Remote setting, event upload, control
- Easy SCADA integration
Focus Areas
| Series | Protection Object | Core Protection Functions |
| AM3SE-I | Feeders, Bus Couplers, Distribution Transformers | Three-stage O/C, Inverse-time O/C, Overload, Three-stage I01/I02 O/C/Inverse, Recloser, Post-acceleration, UFLS, Negative sequence O/C, Non-electric protection, FC Block |
| AM3SE-U | PT Cubicles, Bus Voltage Monitoring | Under voltage alarm, Over voltage alarm, Zero-sequence overvoltage alarm, PT break alarm |
Function
Function (AM3SE-I)
| Function | Description |
| 3–Stage Overcurrent | Three stages (instantaneous, definite time) with under-voltage lockout & 2nd harmonic blocking options. |
| Inverse–Time Overcurrent | IEC standard curves (normal, very, extreme), under-voltage lockout selectable. |
| Overload | Alarm or trip with adjustable threshold and delay. |
| 3–Stage I01 Zero–Seq OC | Three stages for external zero-sequence current (I01), alarm/trip per stage. |
| 3–Stage I02 Zero–Seq OC | Three stages for external zero-sequence current (I02), alarm/trip per stage. |
| I01/I02 Inverse–Time | Zero-sequence inverse-time protection with selectable curves. |
| Negative Sequence OC | Two stages + inverse time, alarm/trip configurable. |
| Recloser | Single-shot auto-reclose with check/no-check options. |
| Post–Acceleration OC | Enabled for 3s after closing, under-voltage lockout optional. |
| I01/I02 Post–Acceleration | Zero-sequence post-acceleration. |
| Under–Frequency Load Shed | UFLS with under-voltage, under-current, and df/dt blocking. |
| Over–Frequency Trip | Trip when frequency exceeds set value. |
| Under/Over Voltage | Alarm or trip based on line voltage. |
| Zero–Seq Overvoltage | Alarm/trip using external or self-produced U0. |
| PT Break Alarm | Detected via negative sequence or voltage/current criteria. |
| Control Circuit Alarm | Alerts on abnormal breaker status (both on/off simultaneously). |
| FC Block | Blocks protection when current exceeds FC threshold (fuse priority). |
| Non–Electric Protection | Up to 10 inputs (over-temp, gas, door, etc.) with independent delays and alarm/trip. |
| Voltage Phase Loss | Detects phase loss based on voltage magnitude and difference. |
| Maintenance Block | Blocks communication or outputs when maintenance DI is active. |
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Function (AM3SE-U)
| Function | Description |
| Under Voltage Alarm | Alarms when all three line voltages drop below the set value. |
| Over Voltage Alarm | Alarms when any line voltage exceeds the set value. |
| Zero–Seq Overvoltage | Alarms using external or self-produced U0. |
| PT Break Alarm | Detects single-phase, two-phase, or three-phase PT break via negative sequence and voltage magnitude. |
Model Selection
| Model | ACInputs | DI | DO | Protocols | KeyFeatures |
| AM3SE-I | 5I + 3U | 11 | 5 | Modbus-RTU, IEC60870-5-103 | Three-stage O/C, Zero/Negative seq., Recloser, UFLS |
| AM3SE-U | 0I + 3U | 11 | 5 | Modbus-RTU, IEC60870-5-103 | Under/Over voltage alarm, Zero-seq overvoltage, PT break |
Specification
| Parameter | Value |
| Auxiliary Power | AC/DC 220V, 110V; DC 48V, 24V (±20%) |
| Power Consumption | ≤10 W (DC) |
| Rated Voltage | AC 100V or 100/√3V |
| Voltage Measurement Range | 1～120V |
| Voltage Accuracy | ±0.5% |
| Rated Current (AM3SE-I) | AC 5A or 1A |
| Current Measurement Range | 0.04In～15In |
| Current Accuracy | ±0.5% |
| Frequency | 50/60 Hz (±0.1 Hz) |
| Digital Inputs | 11 channels, wet contact (voltage specified in order) |
| Digital Outputs | 5 relay outputs (NO) |
| Communication | 1 × RS485, Modbus-RTU / IEC60870-5-103 (selectable) |
| Event Records | >200 events |
| Operating Temperature | -10°C ～ +55°C |
| Storage Temperature | -25°C ～ +70°C |
| Relative Humidity | 5%～95% (non-condensing) |
| Altitude | ≤2500 m |
| Insulation Resistance | >100 MΩ @500Vdc |
| Dielectric Strength | 2 kV between circuits and earth |
| EMC Immunity | Level IV for EFT, ESD, Surge (per GB/T 14598.26) |
| Protection Degree | IP30 (front panel) |
| Dimensions (H×W×D) | 122 × 152 × 100 mm |
| Cut–out | 152 × 122 mm |
| Mounting | Panel flush mounting |
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FAQ
AM3SE-I is the current type, offering full current-based protection (overcurrent, zero-seq, negative seq, etc.) for feeders and transformers. AM3SE-U is the voltage type, dedicated to voltage monitoring and alarms (over/under voltage, PT break) for PT cubicles.
In the “DI Config” menu, enter the corresponding code from the tele-signal mapping table (Appendix 2) to map each DI to a status, non-electric signal, strap, or signal. This allows flexible adaptation to your switchgear wiring.
Yes, the device operates at -10°C to +55°C and can tolerate short-term up to 70°C. For outdoor installations, use a shaded, ventilated enclosure. Conformal coating is available for high humidity/saline environments (please specify when ordering).
The AM3SE supports both Modbus-RTU and IEC60870-5-103, switchable via the menu. It enables remote setting modification, event upload, and remote control, integrating easily with Acrel-2000Z or third-party SCADA.
No, the device does not include an internal anti-pumping circuit. However, it can be used with the optional external AM5-FT anti-pumping module (DIN-rail mount, AC/DC 110V or 220V).
The AM3SE stores over 200 event records, including protection trips and alarms, with time stamps and fault values. This helps with post-fault analysis.
The cut-out is 152×122 mm, shared across the entire AM3SE series. This unified size simplifies panel design and future replacement—no need to modify the cut-out when changing models.
The AM3SE-I provides basic overcurrent and negative-sequence protection, but for comprehensive motor protection (thermal overload, stall, start-up supervision) we recommend the AM5SE-M series.
Summary
The AM3SE series offers a compact, cost-effective, and highly reliable protection solution for 35kV and below terminal substations. With its two model variants—current type for feeder/transformer protection and voltage type for PT monitoring—it covers a wide range of distribution applications. Industrial-grade EMC, flexible DI configuration, and dual-protocol communication ensure robust performance and easy integration. Whether for new installations or retrofitting existing switchgear, the AM3SE series delivers essential protection with simplicity and value.
