The bus bar system incorporates both an isolator and a circuit breaker. When a fault occurs, the circuit breaker trips and isolates the faulty section of the bus bar, allowing it to be disconnected from the rest of the circuit.
Electrical bus bars come in various shapes, including rectangular, cross-sectional, and round. Among these, rectangular bus bars are most commonly utilized in power systems. They are typically made from copper or aluminum.
Common Dimensions of Bus Bars:
· 40×4 mm (160 mm²)
· 40×5 mm (200 mm²)
· 50×6 mm (300 mm²)
· 60×8 mm (480 mm²)
· 80×8 mm (640 mm²)
· 100×10 mm (1000 mm²)
Bus Bar Arrangements: Several types of bus bar arrangements are used in power systems, and the choice of arrangement depends on factors such as reliability, flexibility, and cost. Here are some common arrangements:
1. Single Bus Bar Arrangement: This arrangement is straightforward and involves only one bus bar along with a switch. All substation equipment, including transformers, generators, and feeders, connect to this single bus bar.
Advantages:
· Low initial cost
· Minimal maintenance
· Simple operation
Disadvantages:
· Complete supply interruption in case of a fault
· Limited flexibility, suitable only for small substations where supply continuity isn't crucial
2. Single Bus Bar with Bus Sectionalization: This setup includes circuit breakers and isolators. The isolator disconnects the faulty section, thereby preventing a complete shutdown. It adds a circuit breaker, which slightly increases the system cost.
Advantages:
· Faulty sections can be removed without disrupting supply continuity
· Individual sections can be maintained without affecting the whole system
· Current-limiting reactors reduce fault occurrences
Disadvantages:
· Additional cost due to extra circuit breakers and isolators
3. Main and Transfer Bus Arrangement: This design utilizes two types of bus bars: a main bus bar and an auxiliary bus bar. A bus coupler connects isolating switches and circuit breakers to the bus bars and facilitates load transfer between them during overloading.
Advantages:
· Maintains supply continuity even during faults
· Easy maintenance without disrupting the supply
· Lower maintenance costs
· Bus potential is used for relay operation
· Simple load shifting between buses
Disadvantages:
· Increased cost due to the use of two bus bars
· A fault on any bus can cause a complete shutdown
4. Double Bus Double Breaker Arrangement: This configuration employs two bus bars and two circuit breakers without needing additional equipment like bus couplers.
Advantages:
· Offers high reliability and flexibility
· Supply continuity is maintained as loads can be shifted between buses during faults
Disadvantages:
· Higher cost due to two buses and circuit breakers
· Increased maintenance costs
5. Sectionalized Double Bus Bar Arrangement: This system uses a sectionalized main bus bar and an auxiliary bus bar. Sections of the bus bar can be disconnected for maintenance while connecting to an auxiliary bus bar. However, sectionalizing the auxiliary bus bar is not required as it would increase costs.
6. One and a Half Breaker Arrangement: This arrangement involves three circuit breakers for two circuits. Each circuit uses one and a half circuit breakers, making it suitable for large stations handling substantial power.
Advantages:
· Protects against supply loss
· Bus bar potential is used for relay operation
· Allows easy addition of extra circuits
Disadvantages:
· Complex relaying system
· High maintenance costs
7. Ring Main Arrangement: Here, the end of the bus bar connects back to its starting point to form a ring.
Advantages:
· Provides dual supply paths, reducing the impact of faults
· Limits the fault to a specific section
· Allows maintenance of circuit breakers without interrupting supply
Disadvantages:
· Adding new circuits can be challenging
· Overloading issues if any circuit breaker is opened
8. Mesh Arrangement: In this setup, circuit breakers are installed in a mesh formed by the buses, with circuits tapped from mesh nodes. Controlled by four circuit breakers, it provides protection against bus bar faults but lacks switching capabilities. This arrangement is ideal for substations with numerous circuits.
Disadvantages:
· Faults require opening two circuit breakers, disrupting the mesh
· Limited switching facilities
Each bus bar arrangement has its own set of advantages and drawbacks, and the choice depends on the specific requirements of the power system and its operational needs.