BE1-CDS220 Application
8-3
Motor Protection Logic Scheme
This logic scheme (MOTOR) incorporates the essential differential and overcurrent protection elements
that are ideally suited for large motor protection. The 87 restrained element provides high-speed
differential fault protection. Sensitive instantaneous and time overcurrent, negative sequence elements,
50TQ and 51Q, are incorporated for open phase and phase imbalance protection. High-speed ground
fault protection is accomplished with an instantaneous overcurrent element 50TN, and the 51P and 251P
elements provide motor overload and stall (jam) protection. Further protection, locked rotor protection and
start/run detection for low and high inertia motors, is accomplished using a combination of instantaneous
and time overcurrent phase elements, virtual logic switches, and a speed sensing input from the motor.
The percent-restrained differential protection function is the only function of the 87 protection element
required for this application. Set the pickup of the 2
nd
, 5
th
, and 87 unrestrained functions to 0 (setting
disabled). The 87 unrestrained function has a setting only when the 2
nd
and 5
th
harmonic restraint functions
are set for transformer applications (refer to the discussion in Overview of Preprogrammed Logic
Schemes).
DETAILS OF PREPROGRAMMED LOGIC SCHEMES
The following paragraphs expand on each preprogrammed scheme. The application features of each logic
scheme are broken down into their separate protection elements and described in detail. The integration
of protection and control elements, and alarm elements are also described in detail.
Multifunction protection products are the best thing to happen to the protection industry in the last 30
years. The operating information they provide, along with their flexibility, versatility, and economics,
provide the protection engineer with options that were never available with previous technologies. There
is, however, one cardinal rule that must be followed to ensure continuous, reliable, and secure protection
of the user’s facilities.
Regardless of the product manufacturer, common mode failure is a possibility that the protection engineer
must consider in his design. For example, if a BE1-CDS220 is used to protect a two-winding transformer,
the protection engineer cannot depend on the internal 51 time overcurrent element to backup the primary
differential 87 protection element of the same relay. A common mode failure such as the power supply
could disable the entire relay and leave the transformer with no protection. Also, the self-testing feature of
the product is designed to disable the relay outputs when a problem is detected.
Basler Electric products are among the most reliable in the industry, but we believe that it does not make
good engineering sense to place all your eggs in one basket. That is why Basler strongly recommends
that a second multifunction device be installed to provide independent backup and zone overlapping for
each protected zone. In the transformer example given in the previous paragraph, the 87 protection
element of the BE1-CDS220 would require 51 backup protection from a separate BE1-851 or BE1-951
device. Conversely, a BE1-CDS220 50 or 51 overcurrent element would backup a separate BE1-851 or
BE1-951 zone used for low-side bus protection.
The following paragraphs discuss the protection and control capabilities of each preprogrammed BE1-
CDS220 protection logic scheme. Although it is not discussed in each paragraph, the reader should be
aware that the application of an independent, overlapping, backup zone of protection is recommended for
a complete protection design.
Each preprogrammed protection logic scheme begins with the application intent of the design. Next, the
protection elements are discussed in detail, including CT connections and typical zone and reach
information, followed by protection and control integration, and alarm information specific to the
preprogrammed design. Unique references for each scheme, including one-line and logic diagrams, and
program codes are included.
CAUTION
Never use a protection element from a multifunction relay to backup another
protection element in the same relay!
Содержание BE1-CDS220
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Страница 289: ...BE1 CDS220 Installation 12 7 Figure 12 8 MX Case Horizontal Panel Mount Front View Overall Dimensions...
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Страница 424: ...ii Time Current Characteristics BE1 CDS220 This page intentionally left blank...
Страница 441: ...BE1 CDS220 Time Overcurrent Characteristic Curves A 17 Figure A 13 Time Characteristic Curve A Standard Inverse 99 1621...
Страница 442: ...A 18 Time Overcurrent Characteristic Curves BE1 CDS220 Figure A 14 Time Characteristic Curve B Very Inverse 99 1376...
Страница 443: ...BE1 CDS220 Time Overcurrent Characteristic Curves A 19 Figure A 15 Time Characteristic Curve C Extremely Inverse 99 1377...
Страница 444: ...A 20 Time Overcurrent Characteristic Curves BE1 CDS220 Figure A 16 Time Characteristic Curve G Long Time Inverse 99 1622...
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