DC systems include Rectifier/Charger, Battery Bank, DC Distribution Board (DCDB), and all supporting accessories used as DC power sources for control, protection, communication, and emergency power supply equipment.
1. Applicable Standards
DC systems must meet or refer to the following standards:
- IEC 61000 – Electromagnetic Compatibility
- IEC 60146 – Semiconductor Converters
- IEC 60896 / IEC 61427 – Stationary Lead-Acid or VRLA Batteries
- IEC 60255 – Relay & Protection Equipment Power Supply Requirements
- IEEE 1657 – Maintenance and Testing of Stationary Batteries
- IEEE 446 – Recommended Practice for Emergency Power Systems
2. System Description
The DC system consists of:
- Rectifier/Charger Unit
- Battery Bank
- DC Distribution Board (DCDB)
- Monitoring & Alarm System
The system must be able to provide continuous, stable, and reliable supply for
all critical loads on the installation.
3. System Voltage
- Nominal DC voltage : 110 VDC or 48 VDC (as per the project)
- Voltage tolerance :
- Float Mode: Nominal +2% / -5%
- Boost/Equalize Mode: as per battery manufacturer’s recommendations
- Ripple voltage: < 2% RMS
4. Rectifier/Charger Unit
- General Requirements
- Type: thyristor/IGBT controlled rectifier, industrial grade
- Redundancy: N+1 (if required)
- Efficiency: ≥ 90%
- Power Factor: ≥ 0.95
- Cooling: Natural/Forced as required
- Electrical Parameters
- AC Input Voltage: 380–400 VAC, 3-phase, 50 Hz
- Input Tolerance:
- Voltage: ±10%
- Frequency: ±5%
- Output:
- Steady-state regulation: ±1%
- Protection Features
- AC input MCB
- DC output MCCB
- Reverse polarity protection
- Short circuit protection
- Over-voltage & under-voltage protection
- Charger fail alarm
- Rectifier over-temperature shutdown
- Metering & Indication
- Voltage, current, charger status, battery charging status
- LCD/HMI panel with parameter setting
- 4.5 Communication (optional)
- Modbus TCP/RTU / IEC 61850 gateway
5. Battery Bank
- Battery Type
- VRLA (Valve Regulated Lead Acid) or
- Flooded Lead Acid Industrial Type (as per the project)
- 5.2 General Requirements
- Design life: 10–20 years
- Capacity: according to load needs + autonomy time
- Installation: In rack, ventilated room
- Autonomy Time
- Minimum backup: 2 hours (or as per the project)
- Discharge rate: C10 or C5 according to design
- Battery Protections
- Battery fuse on each string
- Temperature sensor
- Battery Low Voltage (BLV) alarm
- Battery Very Low Voltage cutoff
6. DC Distribution Board (DCDB)
- General Requirements
- Enclosure: IP31/IP41 indoor; IP54 outdoor (as required)
- Busbar material: Copper
- DC MCB/MCCB for outgoing feeders
- Load grouping: Control, protection, communication, auxiliary systems
- Monitoring
- Voltage presence monitoring
- Ground fault detection system
- Positive & Negative busbar monitoring (optional)
7. Control, Monitoring & Alarms
The system must have an alarm:
- Charger fail
- Rectifier fault
- Battery low voltage
- Battery high voltage
- DCDB fuse/MCB trip
- Earth fault (positive/negative)
- AC input failure
- Temperature high
Alarm output:
- Dry contact NO/NC
- SCADA data via communication protocol (if required)
8. Mechanical Construction
- Frame material: Mild steel 2 mm, powder coated RAL7035
- Cooling: Natural ventilation or fans with filter
- Cable entry: top/bottom as required
- Layout must allow easy maintenance & accessibility