It’s indicated from the actual operation of power system that harmonic problem is the primary threat to the safe operation of shunt capacitor.Especially

during HVDC is in monopolar operation

the harmonic current in AC transformer would be increased due to the DC magnetic biasing and be amplified after entering in the operating shunt capacitor.Finally

the shunt capacitor would be damaged.A certain 35 kV reactive power compensating capacitors at 500 kV substation had been exploded in succession because the San-guang HVDC system was monopolar operation.In this paper

the principle of harmonic current coming from monopolar operation of HVDC is introduced

and then the amplified principle and harm to the shunt capacitor are analyzed.Also

reason of the blast of reactive power compensating capacitors at 500kV substation during monopolar operation in San-guang HVDC is analyzed in detail.Finally

some measures are proposed to restrain the amplification of harmonic current.