CHAPTER 8 RELAY TABLE GROUP REPAIR INSTRUCTIONS Section I. INTRODUCTION 8-1.   Scope. a.   Section   I   of   this   chapter   includes   a   brief   des- cription   of   the   assemblies   that   make   up   the   relay   ta- ble   group,   overall   functional   operation,   symptoms   of relay   table   group   malfunction,   and   relay   table   group equipment   tests. b.   Subsequent   sections   of   this   chapter   include repair  instructions  for  the  assemblies  which  are  part of  the  relay  table  group. 8-2.   Relay   Table   Group   Description. a.   The   relay   table   and   related   parts   (fig.   8-1) intrudes   the   control   relay   assemblies,   the   excitation assembly   exciter   and   the   load   measuring   unit.   The load   measuring   unit,   and   the   excitation   assembly exciter   are   common   to   all   modes   and   classes   of   sets. Control  relay  assemblies  include  the  tactical  relay assembly  (used  on  all  sets),  precise  relay  assembly (used  on  Mode  1,  Class  1  sets),  and  two  different special  relay  box  assemblies  (one  used  on  Mode  I sets  and  the  other  used  on  Mode  II  sets). b.   The   tactical,   precise,   and   special   relay   box assemblies   contain   control   relay   modules   for   over- voltage,  short  circuit,  and  reverse  power  on  all sets.  Class  1  sets  also  contain  additional  control relay  modules  for  underfrequency,  undervoltage,  and permissive  paralleling. c.   The   excitation   assembly   exciter   system   pro- vides  control  of  excitation  voltage  to  the  main  gener- ator  to  produce  voltage  buildup  in  the  generator  field coils. The   excitation   system   assembly   contains   a voltage   regulator   that   senses   the   generator   output voltage  and  uses  it  as  a  reference  to  control  field current   in   the   generator   and   thus   regulate   the   gener- ator   output   voltage   level. d.  The  load  measuring  unit  (LMU)  is  supplied  on all   sets.   The   LMU   provides   a   dc   signal   proportional to  the  real  power  (kw)  being  delivered  by  the  main generator.   Refer   to   paragraphs   7-1   and   7-2. 8-3.   Relay   Table   Group   Symptoms   and   Isolation   of Malfunction. Malfunctions   in   the   relay   table   group   will   be   electrical in   nature,   and   will   affect   the   generator   output   voltage, via  the  excitation  system  assembly,  and  normal  sys- tern   operation   due   to   a   malfunctioning   protection   relay in   the   tactical   precise   or   set   special   relay   box   assem- bly.   If   the   set   is   in   operable   condition,   the   equip- ment  tests  listed  in  table  8-1  can  be  performed  to  iso- late   the   malfunction. Section  II.  CONTROL  RELAY  ASSEMBLIES 8-4.   Scope This  section  includes  repair  instructions  for  the  tac- tical   relay   assembly,   precise   relay   assembly,   and special   relay   box   assemblies. 8-5.   Removal. See  figure  8-1,  unscrew  electrical  connectors,  and remove   the   tactical   relay   assembly   (2),   precise   re- lay   assembly   (4),   special   relay   assembly   (14),   ex- citation   assembly   (18),   and   relay   table   (52),   as   re- quired. 8-6.    Disassembly. NOTE Tag  all  electrical  connections  removed during   disassembly   for   position   identi- fication  during  reassembly. a.  Tactical  Relay  Box  Assembly. (1)   See   figure   8-2   and   disassemble   the   tactical relay   assembly   as   follows: (a)  Remove  screws  (1)  and  washers  (1A)  and remove cover (2). (b)   Tag   and   disconnect   all   wiring   harness leads. (c)   Complete   disassembly   in   accordance with  figure  8-2. (2)   See   figure   8-3   and   disassemble   the   tactical relay   resistor   assembly. b.  Precise  Relay  Box  Assembly  (Class  1  Sets). — (1)  On  Class  1,  Mode  1  Sets,  see  figure  8-4  to disassemble  the  precise  relay  box  assembly. NOTE Tag   and   disconnect   all   electrical   leads prior   to   removal   of   wiring   harness   (7). (2)  See  figure  8-5  for  disassembly  of  the  re- sistor   assembly. Change   7   8-1