DSE Model 8620 Main Control and ATS Operators Manual
110
12.2.3 MODBUS
The RS485 output uses Modbus communications protocol. This uses a master-slave technique to
communicate. Only the Master can initiate a packet transaction, called a ‘query’. When appropriate the slave
(8620 Module) responds to the query and provides the information requested by the master.
All supported data can be read and written as specified in the register table (documentation is available from
Deep Sea Electronics Plc.).
When the 8620 Module receives a query it will respond by either supplying the requested register data or
performing the requested action. A slave device (the 8620 module) will never initiate communications on the
Modbus™ link. The 8620 can only be configured as a slave device. The Master can only query individual
slaves. Refer to the Modbus™ protocol document for more details.
12.3 IEEE C37.2 STANDARD ELECTRICAL POWER SYSTEM FUNCTION NUMBERS
The DSE 8620 contains many protection devices and functions, which are listed in detail in the following
sections.
Functions and protections provided corresponding to IEEE C37.2 (1996) system device numbers are listed
below.
.
Overall the 8620 is designated as 11 - Multifunction device and includes the following protections and
functions:
Device Description
2
time delay starting
or closing relay
A device that functions to give a desired amount of time delay before or
after any point of operation in a switching sequence or protective relay
system, except as specifically provided by device functions 48, 62, 79, and
82.
3
checking or
interlocking relay
A device that operates in response to the position of one or more other
devices or predetermined conditions in a piece of equipment or circuit, to
allow an operating sequence to proceed, or to stop, or to provide a check
of the position of these devices or conditions for any purpose.
5 stopping device
A control device used primarily to shut down equipment and hold it out of
operation. (This device may be manually or electrically actuated, but it
excludes the function of electrical lockout [see device function 86] on
abnormal conditions.)
12 overspeed device A device, usually direct connected, that operates on machine overspeed.
14 underspeed device
A device that functions when the speed of a machine falls below a
predetermined value.
15
speed or frequency
matching device
A device that functions to match and hold the speed or frequency of a
machine or a system equal to, or approximately equal to, that of another
machine, source, or system.
18
accelerating or
decelerating device
A device that is used to close or cause the closing of circuits that are used
to increase or decrease the speed of a machine.
25
synchronizing or
synchronism-check
relay
A synchronizing device produces an output that causes closure at zero-
phase angle difference between two circuits. It may or may not include
voltage and speed control. A synchronism-check relay permits the
paralleling of two circuits that are within prescribed limits of voltage
magnitude, phase angle, and frequency.
27 undervoltage relay
A device that operates when its input voltage is less than a predetermined
value.
30 annunciator relay
A non-automatically reset device that gives a number of separate visual
indications upon the functioning of protective devices and that may also be
arranged to perform a lockout function.
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