Section 5 1MAC309294-MB FControl functions338 RER620Technical Manualthe Sectionalizing recloser, the Sectionalizing recloser will open after a program delay toset up for the back feeding from the alternate source. This timer is set to expire prior to theMidpoint and Tiepoint timers.5.4.3.2 Midpoint RecloserThe Midpoint recloser also is normally closed. Unlike the Sectionalizing recloser,however, it does not open in response to phase voltage loss. Instead, it supports loopcontrol by automatically altering the RER620 settings in accordance with changingvoltage conditions. Specifically, upon the expiration of it's under voltage timer, it willswitch to a new setting group to prepare for a back feed condition and for a period will gointo non-reclose mode. The reason for the nonreclose is that in the event the fault isbetween the Sectionalizing unit and the Midpoint, it would be undesirable to have therecloser sequence through multiple operations. Though the reclose blocked condition willchange to normal after a programmed amount of time, the control will stay in New SettingsGroup until the loop scheme is reset.5.4.3.3 Tiepoint RecloserThe Tiepoint recloser, unlike the Sectionalizing and Midpoint recloser is normally open.It closes in response to a loss of all phase voltages from one source if the other source phasevoltages are live. Once closed, the Tiepoint breaker will trip automatically if a downstreamovercurrent condition exists and is not isolated by the midpoint recloser first. The Tiepointrecloser can be set to employ different fault thresholds depending on which side of the loopit is supplying, i.e., which side is downstream. After the close operation, it also is set to gointo non-reclose mode for a period of time in the event the fault is between the Midpointand Tiepoint. If the control changed to New Settings Group for the close operation, it willremain in that setting group until the Recloser is opened and the loop scheme is reset.5.4.4 Operation principleThe Operation setting is used to enable or disable the function. When selected “On” thefunction is enabled and respectively “Off” means function is disabled.The operation of DLCM can be described by using a module diagram (see Figure 179). Allthe modules in the diagram are explained in the next sections.
