Commissioning on-site electrical systems

Overview

Kutsmeda's article adapts ASHRAE Guideline 0's four-phase commissioning process to on-site electrical systems in critical facilities. His central argument is that commissioning must begin in pre-design so that the design supports testing. The article lays out the equipment scope and three test levels: individual equipment, discrete system and integrated system (black-start).

The discrete system level means, for example, testing PDU, UPS and switchgear together under load and on generator. The integrated level covers site-wide black-start with partial failures. The design phase should provide load-bank connections or isolation breakers for phased construction, and control sequences with timer presets for every mode.

In the construction phase, the article notes that factory tests often miss interfaces with controls, mechanical and life-safety systems, so the commissioning authority (CxA) may add witnessed procedures. In a North Carolina data centre case study, a manufacturer-built simulator and phased testing uncovered defective breakers, failure-mode interaction problems and inrush coordination issues.

The commissioned system later rode through a 25 kV utility switch fault without losing critical load; the owner estimated a recovery cost of $5 million had it dropped. The limits of the article are that it rests on a single 2008 case study and that the cost figure is the owner's own estimate. Related documents named are ASHRAE Guideline 0-2005, NETA ATS, IEEE 450, IEEE 1188, NFPA 70E, NFPA 110 and NFPA 111.

Key points

1. Three test levels: individual equipment, discrete system (e.g., PDU+UPS+switchgear under load and on generator) and integrated site-wide black-start with partial failures.
2. The design phase must provide load-bank connections or isolation breakers for phased construction, and control sequences with timer presets for every mode.
3. Factory tests often miss interfaces with controls, mechanical and life-safety systems; the CxA may add witnessed procedures.
4. Case study testing found defective breakers, failure-mode interaction problems and inrush coordination issues.
5. A post-commissioning 25 kV utility switch fault was ridden through without losing critical load.
6. The owner estimated a $5 million recovery cost had the load dropped.

Using it in design

• For phased builds, the tool should place load-bank connection points and isolation breakers and output a Cx test list with individual, discrete and integrated levels.
• Include sequence-of-operations timer presets as fields on transfer and paralleling equipment.
• Involve the commissioning authority from the earliest design stage.
• Define witnessed site tests for interfaces that factory tests do not cover.

Who should read it

Engineers and commissioning authorities who design, commission and test electrical systems for critical facilities.

Related standards

• ASHRAE Guideline 0-2005
• NETA ATS
• IEEE 450
• IEEE 1188
• NFPA 70E
• NFPA 110
• NFPA 111

Publication details

Authors

Kenneth Kutsmeda

Publisher

Consulting-Specifying Engineer

Year

2008

Document language

English

Source type

Expert / community

Access

Free to read

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation