The utility model relates to a reactive power compensation protection device in a power transmission and transformation system, and belongs to the technical field of reactive power compensation in the power transmission and transformation system. According to the technical scheme, multiple single capacitors (11) are connected in parallel to form string sections of a high-voltage parallel capacitor set, and each string section is parallelly provided with a discharge coil (12); a current unit (16) including a current sensor is arranged on the capacitor branch of each single capacitor, and the current unit is connected with a controller (19); the discharge coil is provided with a secondary processing unit, and the secondary processing unit is connected with the controller. The device of the utility model can be used for discharge coil fault protection and sensitive protection of each capacitor, and providing most sensitive protection and fault early warning on the high-voltage parallel capacitor set in the earliest limit, the reuse rate of the reactive power equipment can be improved, operation reliability of the reactive power compensation device is improved, serious fault can be prevented from happening as much as possible, protection sensitivity can be improved, the fault equipment can be timely cut off, and serious fault can be avoided.