ProSoft Technology PLX8X-MNET-61850 - Manual (Page 159)

PLX8x-MNET-61850 ♦ Communication Gateway Reference
Modbus TCP/IP to IEC 61850 User Manual
ProSoft Technology, Inc. Page 159 of 228
May 14, 2014
IEC 61850 MMS Write
This covers the gatewa y’s implementation of IEC 61850-7-2 Clause 17:
CONTROL Class model (Writable Data).
The IEC 61850 driver will be able to write to some IED data attributes. The
writable data attributes will be those that are identified in the ICD file with control
classes of:
 Direct with normal security
 Select Before Operate (SBO) with normal security
 Direct with enhanced security
 Select Before Operate (SBO) with enhanced security
Control with normal security is for data attributes in which the Client will not
receive failure information. This implies that there would not need to be any
action taken by a supervisory control on the system if the value of the data
attribute did
n’t change to the value the IEC 61850 driver was trying to write to it.
The gateway will receive an acknowledgment (ack) telling if the operation worked
or not.
The control function may optionally include a Select step, used to check that the
control may be valid and to eventually lock a resource. SBO-with-normal-security
and SBO-with-enhanced-security include the Select step. This is handled
automatically by the gateway.
IEDs have certain filters in them that check that there will be no damage if the
control is issued. These functions are listed under "System control functions".
 Control unity (on the controlled item, in the bay, in the voltage level, in the
substation).
 Interlock validity: Interlocking is a parallel function that delivers a status to
enable or disable a control (if interlock is set to on). The control message may
contain an interlock violation status to bypass it.
 Synchrocheck validity: When closing a breaker, the synchrocheck will verify
some electrotechnical conditions and enable or disable the control,
depending on its type.
 Time validity: The control contains a time attribute that specifies the time limit
for issuing the control. This avoids issuing an old control that would have
been stacked into the network.
 Locked status: A controlled item may be under lock status when the
substation is partly in maintenance mode. This prohibits any control, for
example, on a breaker if an operator is performing some repair on the line.
Note that locking an item is an example of control.
 Control privilege: This is needed if an operator expects to control an item to
check his privileges.
 Substation and bay mode status: The substation should be in remote mode to
enable remote control (i.e. from SCADA) and in local mode to enable control
issued inside the substation. The bay mode should be in remote mode to
enable control from the station level or remote control level (SCADA).
 State of the controlled item: The control should lead the controlled item into
an authorized state (for example, it is impossible to open an open
disconnecter). When the controlled item is in an unknown state (for example,
double point status have the same value), this filter is optionally suppressed.