A practical Q&A guide for electrical engineers on Nickel Cadmium Pocket Plate batteries in EHV substations, covering specs, construction, and installation..
This article helps electrical engineers understand the design, operation, and requirements of Nickel Cadmium Pocket Plate batteries in EHV substations. These batteries are vital for reliable DC backup and protection in high-voltage environments.
General Questions
What is the main purpose of Nickel Cadmium Pocket Plate batteries in EHV substations?
Nickel Cadmium Pocket Plate batteries provide stationary, vented, rechargeable DC power for indoor installation at EHV substations. They support backup for power supply, protection, and evacuation arrangements, especially in renewable energy and co-generation projects.
What are the key service conditions these batteries must withstand?
These batteries are designed for continuous operation under severe tropical conditions, including:
- Maximum ambient temperature: 50°C
- Minimum air temperature: 3.5°C
- Relative humidity: 10–100%
- Maximum annual rainfall: 1450 mm
- Maximum wind pressure: 150 kg/m²
- Altitude up to 1000 meters
- Seismic level: 0.3g horizontal acceleration
- Humid, moderately hot climate, prone to rust and fungus
- Operating temperature: -10°C to +50°C (continuous), -20°C to +70°C (short period)
Which standards must these batteries comply with?
Batteries must conform to the latest versions of IS 10918 and IEC 60623. Equipment meeting other authoritative standards of equal or better quality is also acceptable, provided differences are clearly documented.
Technical Requirements & Sizing
What are the principal technical parameters and available configurations?
Each battery set is stationary, vented, prismatic, and housed in polypropylene containers. Typical configurations include:
- 220V, 500/300/200 AH (174 cells)
- 110V, 300/200 AH (87 cells)
- 48V, 200/1000 AH (38 cells)
All cells have a nominal voltage of 1.2 V and an end cell voltage of 1.14 V for sizing.
How is battery sizing determined?
Battery sizing is based on the required backup time, capacity at a 5-hour discharge rate at 27°C, and end cell voltage of 1.0 V. The number of cells and total voltage are selected to match the substation’s DC requirements.
Constructional Features
What materials are used for containers and why?
Containers and lids are made from high-strength, alkali-resistant polypropylene or nickel-plated mild steel. These materials provide chemical resistance, rigidity, toughness, and excellent insulation, preventing leaks and ensuring long service life.
How are the positive and negative plates constructed?
Plates are made from perforated, encapsulated, nickel-plated steel pockets filled with active mass. This design avoids powder shedding and promotes good interaction between the electrolyte and active material, ensuring durability under fluctuating loads.
What are the requirements for separators?
Separators are micro-porous, alkali-resistant, and chemically inert, providing high insulation to prevent short circuits. They maintain dimensional stability and resist swelling or shrinking during operation.
How are connectors and fasteners designed for safety and reliability?
Connectors use nickel-plated steel or stainless steel, with a minimum nickel coating thickness of 0.01 mm. All terminals and interconnectors are fully insulated or have insulation shrouds—no bare connectors are allowed. End take-off connections use multi-stranded copper cable, and necessary supports and lugs are supplied for termination.
Installation and Operation
What installation considerations are important for these batteries?
Proper air circulation between cells is essential for heat dissipation. Containers must be robust enough to withstand transport, storage, and handling. Vent-plugs with flame arrestors are required for safety, and the design must allow easy monitoring of electrolyte levels.
Are all parts interchangeable and easy to maintain?
Yes, all similar and removable parts are designed to be interchangeable. The equipment is supplied complete with all necessary components for effective and trouble-free operation, even if not explicitly listed in the specification.
Takeaway
Nickel Cadmium Pocket Plate batteries are engineered to deliver reliable DC backup in challenging substation environments. Understanding their technical requirements and construction helps ensure safe, efficient, and long-lasting operation in EHV power systems.
Bonus: Practical Tips for Engineers
For battery sizing, consider both nominal and end cell voltages for reliable backup.
Always check compliance with IS 10918 or IEC 60623 before procurement.
Ensure all connectors are fully insulated to prevent accidental shorts.
Regularly inspect electrolyte levels and container integrity.
Provide adequate ventilation during installation for optimal heat dissipation.
Use only manufacturer-approved spares and accessories for maintenance.
