The responsibility for developing, programming, and testing the sequence of operation for an MTM-TT-MTM switchgear setup depends on a few factors, but generally breaks down like this

General Responsibilities
Overall System Design and Sequence of Operation (SOO)

The ultimate responsibility for defining what the MTM-TT-MTM switchgear needs to do lies with the

system owner/end-user and their engineering consultants. They specify the functional requirements, protection philosophy, interlocking schemes, and desired response to various events. This is documented in a detailed sequence of operation (SOO) document. PLC Programming and Logic Implementation

The responsibility for how to translate the SOO into a working PLC program and logic resides with the

PLC programmer/integrator who usually works for or contract to either gear manufacturer or end user. Factory Acceptance Testing (FAT)

FAT usually requires testing of the MTM sequence of operation with simulation. It is typically a responsibility of a

gear manufacturer with participation from the end user and/or their engineering consultants. Site Acceptance Testing (SAT)

SAT is usually required once the gear is installed at site and testing of sequence of operation with the real life signal and parameters is required. It is typically a combined responsibility of a

gear manufacturer and end user.

Breakdown of Responsibilities1. System Owner/End-User & Engineering Consultants



Defining the Sequence of Operation (SOO)

This is the MOST important step. They must clearly document: All operating modes and scenarios. Interlocking requirements between the Main-Tie-Main (MTM) breakers and the Tie-Tie (TT) breaker. Protection settings and coordination. Response to faults, loss of power, etc. Manual and automatic operation requirements. Communication requirements with SCADA or other systems.

Reviewing the PLC Logic

They are responsible for understanding the programmed logic and ensuring it accurately reflects the intended SOO.

Participating in FAT and SAT

They verify that the system operates as designed.2.

Switchgear Manufacturer



Providing the Switchgear Hardware

This includes the breakers, control panels, protective relays, communication interfaces, and any other necessary equipment.

PLC Programming (Often)

In many cases, the switchgear manufacturer will also be responsible for the PLC programming, especially if they supplied the PLC and control system. However, this can also be contracted out.

Factory Acceptance Testing (FAT)

The manufacturer performs comprehensive testing at their facility to verify the functionality of the switchgear before it is shipped to the site. This should include testing the MTM-TT-MTM sequence of operation. This is often done with simulations of inputs (e.g., voltage loss, breaker trip signals) to prove the logic.

Providing Documentation

The manufacturer provides detailed documentation, including schematics, wiring diagrams, PLC program documentation, and testing reports.

Site Acceptance Testing (SAT) Support

The manufacturer typically provides support during site commissioning and testing. This may involve on-site engineers to troubleshoot issues and verify proper operation.3.

PLC Programmer/Integrator



PLC Programming

Responsible for writing, documenting, and testing the PLC program that implements the MTM-TT-MTM sequence of operation based on the SOO provided by the system owner/end-user and their engineering consultants.

Integration with Relays and Other Devices

Ensuring that the PLC correctly communicates with and responds to signals from the protective relays, breakers, and other devices in the system.

Troubleshooting and Optimization

Addressing any issues identified during testing and optimizing the PLC program for performance and reliability.

Where the Testing Happens Factory Acceptance Testing (FAT)

Performed at the switchgear manufacturer's facility. Simulates real-world conditions using test equipment. Verifies the correct operation of the switchgear, PLC logic, and protective relays. Provides an opportunity to identify and correct any issues before the switchgear is shipped to the site.

Site Acceptance Testing (SAT)

Performed at the installation site after the switchgear is installed and connected. Uses actual system inputs and outputs. Verifies the proper operation of the switchgear in the real-world environment. Confirms that the system integrates correctly with other equipment and systems. Includes functional testing of the MTM-TT-MTM sequence of operation, including manual and automatic transfer schemes.

In summary

The end-user and their consultants define the requirements (SOO). The PLC programmer translates those requirements into a working PLC program. The manufacturer builds the equipment and often does the PLC programming as well. The manufacturer performs FAT to verify the equipment works according to the SOO and PLC program. All parties participate in SAT to verify the installed system operates correctly in the field.

Important Considerations



Clear Communication

Clear and consistent communication between all parties is essential for a successful project.

Well-Defined Scope of Work

The responsibilities of each party should be clearly defined in the project specifications and contracts.

Detailed Documentation: Comprehensive documentation is critical for testing, commissioning, and future maintenance.It's crucial to review the specific contract and specifications for your project to understand the exact allocation of responsibilities. Don't assume anything; clarify everything upfront. Flag for review