The paper analyzes the various integrated schemes and key constraint conditions of integration

and makes inclusion of experience of integrated equipments. The scopes of secondary functions integration are constrained by some restrictive conditions like hardware

abilities of anti-electromagnetic interference capability

operation and maintenance management. Among these

operation and maintenance management is the key factor which restricts integration of secondary functions. After integration

the ascription of maintenance responsibility is not clear. And functions influence each other

especially in cases that one function may be abnormal or other functions may be affected by overhaul. These problems imply unknown security risks

reducing the reliability and availability of power system.