Current Transformers for Protection Relays

By Morrison Hershfield|Mar 25, 2019 12:00:00 AM

Current transformers for protection relays, as opposed to those use strictly for metering purposes, have an IEEE standard classification. There are two classifications, Class T CTs and Class C CTs. The ‘T’ stands for “tested” and the ‘C’ stands for “computed”.

Class T CTs generally have a high level of flux leakage (due to the way the primary is configured as multiple windings around the core) which requires the performance of the CT to be tested. Class T CTs are rarely used for commercial power system protection relays, and they will not be discussed further here.

Direct Current Isolated-Parallel UPS Systems

By Morrison Hershfield|Nov 19, 2018 1:07:00 PM

This White Paper describes The Isolated-Parallel (“Iso-Parallel” or “IP”) configuration for rotary diesel UPS systems.

PUE Calculations: The Model and the Myths

By Morrison Hershfield|Jun 21, 2013 1:09:00 PM

This White Paper explores some of the more common Power Usage Effectiveness (PUE) calculation mistakes and myths while demonstrating their impact on PUE values calculated for a specific data center facility design project.

Electrical Load Bank Planning: Best Practices for Cx Testing

By Morrison Hershfield|May 3, 2013 1:03:00 PM

The use of load banks, portable or permanent, during the commissioning process to simulate encountered electrical loads has many facets.  Loads banks provide electrical loading (kW) as well as mechanical loading (BTU’s).  

Switchboard Circuit Breaker Remote Operation and Racking

By Morrison Hershfield|Apr 22, 2013 1:11:00 PM

Operation and maintenance of power circuit breaker equipment involves exposure to potential hazards associated with high-energy electrical supply systems which are typically encountered within data centers.  Switchboard accessory mechanisms are available to provide safety when interacting with this equipment.  

Containment Strategies for Co-Location Data Centers

By Morrison Hershfield|Mar 15, 2013 12:00:00 AM
Arrangement of IT equipment cabinets to maintain dedicated hot and cold IT equipment cabinet aisles has long been considered a basic element in computer room cooling design. Thus, a move toward isolating these hot and cold aisles to eliminate mixing of the cold (supply) and hot (return) air streams seems a natural progression as the industry strives for more energy efficient cooling methodologies. Containment in a purpose-built data center, where an owner can maintain some level of control over IT cabinet configurations, is generally fairly straight forward.  However, implementing containment in a co-location data center environment brings with it a unique set of challenges.

Electrical Metering Issues During Commissioning

By Morrison Hershfield|Feb 22, 2013 10:49:00 AM

Electricity unlike anything else is not something that can be seen, like the flow of water. Nor can it be smelt, like the breeze bringing odors. It can however certainly be felt usually with disastrous results.  As humans we rely on the five senses of sight, smell, touch, taste, hearing – electricity in general defies the ability to use most of those senses directly. We can however indirectly observe electricity through the use of meters to determine the presence of it.

Optimizing Existing Data Center Chilled Water Plants

By Morrison Hershfield|Jan 25, 2013 1:08:00 PM

This White Paper describes factors to be considered when optimizing an existing data center chilled water plant.

Current Direct Isolated-Parallel Redundancy: A New and Better Approach to Large Critical Power Systems

By Morrison Hershfield|Jun 3, 2009 1:05:00 PM

This White Paper describes a new approach to large critical power system configuration, which offers significant advantages over current practice for a broad range of commercial applications.


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