The utility model relates to a novel complete set protection device of transformer neutral point, its characterized in that: supporting insulator and temperature sensitive isolator are connected to the arrester lower extreme, and temperature sensitive isolator passes through counter ground connection, the upper end electricity of arrester is connected with the left end stainless steel round stick in excellent clearance, and mating right -hand member stainless steel round stick is connected with the base through current transformer. During normal operating, residual voltage of an arrester is less than excellent clearance thunder and lightning and operation discharge voltage lower limit, frequently discharges the condition that leads to main transformer unnecessarily to trip and will shown and improve in excellent clearance when the thunder and lightning invade. The action current curve of temperature sensitive isolator is less than the arrester power frequency and endures characteristic curve, in case local system splitting appears for non -effective grounding system's accident condition, the action of temperature sensitive isolator, and the cutting is ignited to temperature sensitive component promptly, breaks away from fast and falls, and the arrester is kept apart by supporting insulator and system, has the safety of excellent clearance protection transformer neutral point, does not influence the service reliability index.