For more information on the basics of transformer protection, download our Transformer Protection Application Guide. This
guide was prepared to assist in the selection of relays to protect power transformers. The purpose of each relay is described and related to one or more power system examples.
BE1-CDS240 - Current Differential System with Voltage
The BE1-CDS240 is a compact, feature-packed powerhouse – allowing you to fit state-of-the-art protection, monitoring, and control into virtually any existing panel. The CDS240 provides a unique retrofit package that can fit in cutouts for most Westinghouse and GE 2-winding electromechanical differential relays.
Horizontal rack and panel mount configurations make new-panel applications a snap too. The CDS240 can be ordered with 2, 3, or four sets of current restraint inputs, and onboard DNP is available as an
The BE1-CDS240 includes a 3-phase voltage input. The ability to measure voltage in addition to current opens up a number of new possibilities, which are exploited in the CDS240. In addition to
overcurrent (50/51) and current differential (87) protection, it also offers overvoltage (59), undervoltage (27), frequency (81), and overexcitation (24) protection elements. The presence of voltage
measurements also makes possible additional metering capabilities, such as Watt/VAR and Power Factor calculation.
The BE1-CDS240 provides up to 15 contact outputs or up to 12 contact inputs, plus dedicated trip circuit monitors for up to four breakers.
BESTCOMS, Basler’s state of the art graphical user interface software, significantly reduces setup and commissioning time by offering an easy to use
Windows® based package. Programming procedures that take days with other products can be completed and documented in a matter of hours using the capabilities of BESTCOMS for the
Commissioning assistance is provided through various metering screens of the HMI and a user initiated differential check record that provides a detailed analysis of the installation.
For more in-depth discussions of Transformer Protection issues, see:
Current Transformer Errors and Transformer Inrush as Measured by Magnetic, Optical and Other Unconventional CTs - This paper will review the errors in secondary current for these primary current conditions, provide means of determining when CTs are at risk, and show, using numerical analysis results, the output of a saturated CT. The second part will review the various types of current sensors available on the market, including conventional, hybrid, and optical sensors.
Predicting Current Differential Relay Tripping and Targeting when Testing at Final Settings describes the issues associated with testing at final settings and gives instructions on applying an associated spreadsheet, “Transformer Differential Calculations”.
Solutions for Unconventional Connection of Transformer Differential Current Transformers – This paper is a primer on analyzing unconventional current transformer polarity connections and how to obtain the right connection to achieve the desired direction of operation or polarity as indicated in protective relay manufacturers’ literature.
Three Phase Transformer Winding Configurations and Differential Relay Compensation - This paper reviews the possible winding configuration and gives examples of the nomenclature used with them and how the various phase shifts are created. Plus, it will show how a transformer differential relay compensates for the effects of the various transformer winding configurations.
Using Iop Characteristics to Troubleshoot Transformer Differential Relay Misoperation - This paper explores the issues contributing to transformer differential false trips, and suggests methods to alleviate this issue.