How to Select a Generator Synchronization Panel: A Practical Guide

Introduction

Selecting a generator synchronization panel involves more than choosing a controller brand or panel size. Several factors determine the correct configuration: the number of generators, voltage and capacity, governor and AVR compatibility, and whether the system operates in island mode or parallel with the utility.

Some engineers focus only on the controller and overlook load-sharing requirements or future expansion. Others select a panel based on generator capacity alone and later discover compatibility issues during commissioning.

This guide walks through the key selection factors. Use it as a reference when specifying a synchronization panel for your next project.

In Generator Synchronization Panel Selection, the suitable unit shall be chosen based on generator configuration, electrical system, operating mode and control requirements, rather than merely panel price or controller brand.

What Should You Evaluate When Selecting a Generator Synchronization Panel?

A generator synchronization panel is a control assembly that safely connects a generator to a live bus or utility grid. It matches voltage, frequency, and phase angle before closing the breaker.

What Functions Should Be Considered During Panel Selection?

• Voltage matching
• Frequency matching
• Phase-angle matching
• Phase-sequence checking
• Breaker closing control
• Generator paralleling
• Load sharing
• Generator start/stop control

For generator synchronization details, please see the relevant section.

When Do Generator Requirements Determine the Panel Configuration?

• Two or more generators operating in parallel
• Common bus operation
• Standby generator systems
• Prime power systems
• Generator-to-grid operation
• Capacity expansion
• Critical power systems (data centers, hospitals)

Generator Synchronization Panel vs. Generator Paralleling Panel

Some engineers use these terms interchangeably. They are related but distinct.

Function	Synchronization	Paralleling
Voltage matching	✓	—
Frequency matching	✓	—
Phase-angle matching	✓	—
Breaker closing	✓	✓
Load sharing	—	✓
Multiple generators on common bus	—	✓

Synchronization is the process that makes safe paralleling possible. Paralleling covers the complete operation of generators connected to the same electrical bus.

8 Key Factors in Generator Synchronization Panel Selection

The generator synchronization panel selection process should start with the electrical system and operating requirements.

1. Number of Generator Sets

The number of generators determines the complexity of synchronization, breaker control, communication, and load-sharing logic.

Typical system sizes:

System Size	Generator Quantity	Typical Application
Small	2–3	Commercial / Industrial
Medium	4–8	Factory / Hospital
Large	9–16	Data Center / Mining
Extra Large	16+	Power Plant / Microgrid

Consider future expansion. A system designed for 4 generators today may need to support 6 or 8 in the future. Select a controller platform that supports additional units without replacing the entire panel.

Most modern controllers support up to 16 or 32 generators on a single bus.

2. Generator Rated Power, Voltage, and Frequency

The panel must match the generator’s electrical parameters. Provide these specifications to your supplier:

Parameter	Typical Values
Generator rating	100 kVA – 3000+ kVA
Rated voltage	400V / 415V / 440V / 6.3kV / 10.5kV
Frequency	50Hz / 60Hz
Rated current	Depends on generator capacity
Power factor	Typically 0.8
Short-circuit level	Determines breaker rating

3. Generator Controller Compatibility

Controller compatibility must be confirmed before the panel is finalized.

Generator Controller

The generator controller manages start/stop, engine protection, and basic electrical protection. The synchronization panel must interface with the existing controller. Common controller brands include Deep Sea Electronics, ComAp, and SmartGen.

Governor Interface

The synchronizer adjusts engine speed through the governor. Interfaces include:

• CANbus (J1939) – electronic engines
• Analog (0–10V or 4–20mA) – mechanical or older engines
• Magnetic pickup (MPU) – speed sensing

AVR Interface

The synchronizer adjusts generator voltage through the AVR. Interfaces include:

• CANbus (J1939)
• Analog (0–10V)
• Digital communication

4. Automatic or Manual Synchronization

Synchronization Mode	Best For
Automatic	Industrial and commercial systems
Manual	Operator-controlled systems, commissioning
Automatic + manual backup	Critical power applications

Automatic synchronization uses a digital controller to handle the entire paralleling process. The controller checks voltage, frequency, phase sequence, phase angle, and slip frequency before closing the breaker.

Manual synchronization requires an operator to observe a synchroscope and initiate breaker closure. This mode is useful for maintenance, testing, or emergency scenarios.

Most modern systems use automatic synchronization with manual override capability.

5. Load-Sharing Requirements

Synchronization connects generators to the same bus. Load sharing controls how load is distributed after paralleling.

kW Load Sharing

The controller adjusts the engine governor to share active power (kW) proportionally based on generator ratings. Two methods exist:

• Isochronous – all generators maintain exact frequency, proportional kW sharing
• Droop – frequency drops slightly with load, stable without inter-unit communication

kVAR Load Sharing

The controller adjusts the AVR to share reactive power (kVAR) proportionally. This maintains stable voltage and prevents circulating currents.

Equal vs. Proportional Load Sharing

Equal sharing – identical generators share load equally. Proportional sharing – generators of different ratings share load in proportion to their capacity.

Load-Dependent Start/Stop

Advanced systems automatically start additional generators when load exceeds a threshold and stop them when load drops. This improves fuel efficiency and reduces wear.

6. Generator-to-Generator or Generator-to-Grid Synchronization

Generator-to-Generator Synchronization

Used in island systems where generators operate independently from the utility. Common in factories, hospitals, data centers, mining, and remote power systems.

The first generator to reach rated voltage and frequency closes to the dead bus. Subsequent generators synchronize to the running bus and close their breakers.

Generator-to-Grid Synchronization

Connecting generators to a live utility grid is more complex. The generator must match the grid’s voltage, frequency, and phase angle exactly.

Additional requirements:

• Utility interconnection protection
• Reverse power protection
• Import/export control
• Power factor control
• Loss of mains detection (ROCOF and vector shift)
• Grid code compliance

7. Protection and Synchronism Check Functions

The synchronization panel must include essential protection functions.

ANSI Function	Purpose
25	Synchronism check – prevents out-of-phase closing
27	Undervoltage protection
59	Overvoltage protection
81	Over/underfrequency protection
32	Reverse power protection
50/51	Overcurrent protection

Why Is ANSI 25 Important?

The ANSI 25 relay prevents the breaker from closing when synchronization conditions are outside permitted limits. A 12-degree angular difference during synchronization can apply 1.5 per unit (150% of full load) torque on the generator shaft. This can damage the generator, coupling, and connected equipment.

The ANSI 25 relay provides independent supervision, verifying that voltage, frequency, and phase angle are all within safe limits before permitting breaker closure. Most manufacturers recommend limiting out-of-phase synchronizing to no more than 10 degrees maximum.

8. Communication, HMI, and SCADA Requirements

Modern synchronization panels integrate with building management and SCADA systems.

Common Communication Protocols

• RS-485
• Modbus RTU / Modbus TCP
• Ethernet
• CANbus
• IEC 61850

Integration With SCADA and BMS
Verify the panel supports:

• Remote monitoring and control
• Alarm and trip status reporting
• Event records and fault records
• Measured values (kW, kVAR, voltage, current, frequency)

Selecting the Right Synchronization Panel Configuration

Typical Generator Synchronization Panel Components

Component	Main Function
Synchronization Controller	Synchronizes generator to bus
Generator Controller	Manages start/stop and engine protection
PLC	Executes control logic
HMI	Local operation and monitoring
Circuit Breaker	Connects generator to bus
CT/PT	Current and voltage measurement
Protection Relay	Electrical protection
AVR Interface	Voltage control
Governor Interface	Speed control
Communication Module	SCADA/remote monitoring

How to Select the Right Generator Synchronization Panel Configuration

For 2-Generator Systems

Two generators can operate in parallel for redundancy or increased capacity. The panel typically includes:

• Automatic synchronizer
• Load-sharing control
• ANSI 25 sync-check
• Basic protection functions

For Multi-Generator Systems (3–8+)

More generators require more complex control logic:

• Multiple synchronizers or master controller
• Advanced load-sharing control
• Generator sequencing (start/stop by load demand)
• SCADA communication

For Standby Generator Systems

Generators start automatically when utility fails. The panel includes:

• Automatic start and synchronization
• Load-sharing control
• Automatic transfer switch interface
• Protection functions

For Prime Power Systems

Generators are the primary power source. The panel includes:

• Continuous load-sharing control
• Generator sequencing
• Fuel management
• Remote monitoring

For Generator-to-Grid Applications

Generators parallel with the utility grid. The panel includes:

• Grid synchronization capability
• Import/export control
• Loss of mains protection
• Grid code compliance

Generator Synchronization Panel Selection Checklist

Electrical Parameters

• [ ] Number of generators
• [ ] Generator kW/kVA rating
• [ ] Rated voltage
• [ ] Frequency (50Hz or 60Hz)
• [ ] Rated current
• [ ] Short-circuit level

Control Requirements

• [ ] Automatic synchronization
• [ ] Manual synchronization
• [ ] Load sharing (kW and kVAR)
• [ ] Generator sequencing
• [ ] Governor interface type
• [ ] AVR interface type

Protection

• [ ] ANSI 25 synchronism check
• [ ] Overcurrent protection
• [ ] Earth fault protection
• [ ] Over/undervoltage
• [ ] Over/underfrequency
• [ ] Reverse power protection

Communication

• [ ] HMI local operation
• [ ] PLC control
• [ ] SCADA integration
• [ ] Modbus protocol
• [ ] Ethernet connectivity
• [ ] Remote monitoring

What Information Should You Provide When Requesting a Quote?

Providing these details allows the supplier to recommend a synchronization panel configuration based on actual project requirements.

Required Information	Example
Generator quantity	4
Generator rating	500 kVA each
Voltage	400 V / 415 V
Frequency	50 Hz
Generator type	Diesel or gas
Generator controller	Model/brand
Governor	Model/interface
AVR	Model/interface
Breaker rating	800 A
Operating mode	Standby / Prime
Grid parallel	Yes / No
Load sharing	Required
SCADA	Required
Communication	Modbus TCP
Installation	Indoor / Outdoor
SLD	Required

Common Mistakes in Generator Synchronization Panel Selection

Selecting the Panel Based Only on Generator Capacity

Generator capacity is one factor, but controller compatibility, load sharing, and protection requirements matter equally.

Choosing the Controller Before Defining the System

The controller must match the generator’s governor, AVR, and communication requirements. Define the system first, then select the controller.

Ignoring Governor and AVR Compatibility

Incompatible interfaces cause synchronization failures. Verify the synchronizer can communicate with the existing governor and AVR.

Forgetting Load-Sharing Requirements

Synchronization alone does not ensure stable parallel operation. Load-sharing control is essential for multi-generator systems.

Not Considering Future Generator Expansion

A system designed for 4 generators may need to support 6 in the future. Select a controller platform that supports expansion.

Treating Synchronization and Load Sharing as the Same Function

Synchronization matches parameters before closing the breaker. Load sharing controls load distribution after paralleling. Both are required for stable parallel operation.

Failing to Provide a Single-Line Diagram

The SLD shows the system configuration and is essential for accurate panel design. Always provide an SLD when requesting a quote.

How to Compare Synchronization Panel Suppliers

When evaluating suppliers, consider these factors.

Technical Scope

• Number of generators supported
• Voltage and current range
• Synchronization functions
• Load-sharing capability
• Protection functions

Generator Controller Compatibility

Does the supplier support the specific controller, governor, and AVR models used in your generators?

Engineering and Customization

Can the supplier customize the panel for your specific requirements, or do they only offer standard configurations?

Factory Testing and FAT

Does the supplier conduct factory acceptance testing (FAT) before shipment? This reduces commissioning issues.

Commissioning and Technical Support

Does the supplier provide on-site commissioning support? What is their response time for technical issues?

Documentation

The supplier should provide:

• Single-line diagram (SLD)
• Wiring diagrams
• General arrangement (GA) drawings
• Bill of materials (BOM)
• I/O list
• FAT documents
• Operation manual

Generator Synchronization Panel Selection Example

Example: 4 × 500 kVA Diesel Generators

Project Requirements:

• 4 diesel generators, 500 kVA each
• 400 V, 50 Hz
• Common bus configuration
• Automatic synchronization
• Automatic load sharing
• Standby operation (island mode)
• SCADA communication

Recommended Configuration:

Component	Selection Reason
Automatic synchronizer	Required for automatic parallel operation
Generator controllers	Match existing generator models
Load-sharing control	Proportional kW and kVAR sharing
ANSI 25 sync-check	Safety protection for all synchronizations
Overcurrent and earth fault protection	Basic electrical protection
HMI touchscreen	Local monitoring and control
PLC	Control logic and sequencing
Modbus TCP communication	SCADA integration
Indoor enclosure	IP54 protection

This configuration supports automatic starting, synchronization, load sharing, and remote monitoring. The system can operate with 2, 3, or 4 generators running depending on load demand.

Frequently Asked Questions

What Information Is Needed to Select a Synchronization Panel?

Required information includes generator rated power, rated voltage, frequency, operating mode, synchronizing mode, protection demands and communication protocol requirements.

How Does Generator Quantity Affect Synchronization Panel Selection?

Most modern controllers support 2 to 32 generators on a single bus. Some systems support more with expanded configurations.

What parameters are checked during generator synchronization?

Voltage, frequency, phase angle, and phase sequence are checked. Slip frequency is also monitored to ensure proper closing timing.

What is the difference between synchronization and paralleling?

Synchronization is the process of matching parameters before closing the breaker. Paralleling is the ongoing operation of multiple generators connected to the same bus.

Does a synchronization panel support load sharing?

Yes. Most modern synchronization panels include load-sharing control for both kW and kVAR.

Can generators synchronize with the utility grid?

Yes, with appropriate control and protection functions. Generator-to-grid synchronization requires grid code compliance and loss of mains protection.

Should ANSI 25 Synchronism-Check Protection Be Included?

ANSI 25 is the synchronism check relay. It prevents breaker closure when synchronization conditions are outside safe limits.

What information is needed to select a synchronization panel?

Generator quantity, rating, voltage, frequency, controller type, governor and AVR interfaces, operating mode, communication requirements, and a single-line diagram.

Conclusion

The right generator synchronization panel selection starts with the complete electrical and operating requirements of the generator system.

Follow these steps:

1. Determine the number of generators
2. Confirm generator ratings and voltage
3. Verify governor and AVR compatibility
4. Choose automatic or manual synchronization
5. Define load-sharing requirements
6. Select required protection functions
7. Determine grid-parallel requirements (if any)
8. Specify communication and SCADA needs
9. Plan for future expansion

The right generator synchronization panel is not simply the panel with the most features. It is the panel whose synchronization, control, protection and communication capabilities match the actual generator system and operating requirements.

If you are planning a multi-generator or generator-paralleling system, provide the generator ratings, controller models, breaker information and single-line diagram to obtain a configuration matched to your project requirements.

References

1. IEEE Standard C37.91-2021 – Guide for Protecting Power Transformers.
2. IEEE Transactions on Industry Applications – Art of Generator Synchronizing, Vol. 53, Issue 1, Jan.-Feb. 2017.
3. IEC 60909-0 – Short-Circuit Currents in Three-Phase AC Systems.
4. ANSI/IEEE Standard C37.2 – Electrical Power System Device Function Numbers.
5. IEC 60255 Series – Measuring Relays and Protection Equipment.
6. IEC 61850 – Communication Networks and Systems for Power Utility Automation.
7. Deep Sea Electronics – DSE8610 MKII Synchronization and Load Sharing Controller Technical Specification.
8. ComAp – InteliGen 200 Generator Controller Datasheet.
9. SmartGen – HGM9510 Generator Controller Technical Manual.
10. Eaton – Generator Paralleling Switchgear Design Guide DG027001EN.